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Too much compression. adjusted the valves and it got worse
#1
2ball
2ball
Briggs & Stratton
17.5hp Intek IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
17.5hp Intek IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#2
B
Bertrrr
B
Bertrrr
Not sure what motor you have but you only set the valves when they're in the closed position at TDC or thereabouts doesn't have to be exactly , Set your exhaust at .008 and intake at .006 to start , roll it by hand and get it to repeat and they're set . There is a real possibility that it's stuck in a odd position like exactly Bottom Dead Center and it needs to rock past that point to roll again, the pull cord will not do it ( might break ) Use a pair of pliers or something and roll the pully by hand until it gets past that point and it should roll over fine then - Pull your Plug and stick a skinny screw driver or rod to verify what I'm saying
Post Model and HP of the engine so the brain trust can chime in.
Post Model and HP of the engine so the brain trust can chime in.
#3
I
ILENGINE
I
ILENGINE
Intake valve which is the bottom valve is set to .003-.005 and the exhaust or top valve is set to .005-.007. Normal proper procedure is to turn the engine by hand with the plug out until the piston TDC with both valves closed and then turn the flywheel to were the piston is 1/4 inch down from TDC. The unscientific method is to turn the engine until one valve is open and then adjust the closed valve and then turn until that open valve is closed the the previous one you adjusted is open.
#4
2ball
2ball
ok, so I probably goofed up the gap. I will re-do it tomorrow.
I also need to check the movement of the intake valve. thinking back, I do not think it was moving like the top valve.
I also need to check the movement of the intake valve. thinking back, I do not think it was moving like the top valve.
#5
2ball
2ball
I am pretty sure I understand how to adjust the valves. I am good with that.
So after watching a couple videos, I am wondering if the compression release and cam shaft are not working properly.
when starting the engine it gets caught up on the compression stroke. I need to double check, but I think the bottom valve does not move like the top valve.
The engine is almost 20 years old and I got it used.
Could I have a cam shaft/ compression release issue? How would I know for sure?
So after watching a couple videos, I am wondering if the compression release and cam shaft are not working properly.
when starting the engine it gets caught up on the compression stroke. I need to double check, but I think the bottom valve does not move like the top valve.
The engine is almost 20 years old and I got it used.
Could I have a cam shaft/ compression release issue? How would I know for sure?
#6
R
Rivets
R
Rivets
I can tell you are new to this repair game so I’ll give you a bit of advice. First, stop with the u-tube videos, the guy you referred to, in your first post, shouldn’t be allowed to post. Second, you would do a lot better off finding an online service manual and down load it. Personally I don’t go after ACR until I’ve ruled out everything else. I don’t open up engines unless I have to. Just the thoughts of a retired and tired instructor.
#7
2ball
Oh and Chickanic on Youtube says I may have a Camshaft issue!
2ball
I appreciate the wisdom. I am new to the game. I have fumbled my way through an engine swap, a needle and seat issue, battery issues, tire issues, some unknown gas leak and all have been accomplished mostly through this site and some You-Tube videos. While I am not exactly sure I have a cam shaft issue I hope to find out today or tomorrow. I do like working on these engines and think I could pull off a cam shaft change, or not, we will see!I can tell you are new to this repair game so I’ll give you a bit of advice. First, stop with the u-tube videos, the guy you referred to, in your first post, shouldn’t be allowed to post. Second, you would do a lot better off finding an online service manual and down load it. Personally I don’t go after ACR until I’ve ruled out everything else. I don’t open up engines unless I have to. Just the thoughts of a retired and tired instructor.
Oh and Chickanic on Youtube says I may have a Camshaft issue!
#8
sgkent
sgkent
pull the spark plugs and see if it turns over easy. If so then the problem is too much compression. Adjusting the valves isn't likely to change that much, in fact if they were tight then you might end up with more compression. If it still binds with the plugs out then you have some other kind of problem. And it fuel squirts out the plug hole then it was hydrolocked with fuel bleeding past the carb(s).
#9
2ball
2ball
When I removed the spark plug to turn the engine by hand, it turned easier. The spark plug was not wet. In the past I had a needle and seat issue and I installed a fuel shut off. When I replaced the needle and seat I still used the fuel shutoff every time I turn the mower off (I even run it out of gas just to be extra safe). I don't think I have a hydrolock issue anymore. I will make sure it turns over with the spark plug removed tomorrow.pull the spark plugs and see if it turns over easy. If so then the problem is too much compression. Adjusting the valves isn't likely to change that much, in fact if they were tight then you might end up with more compression. If it still binds with the plugs out then you have some other kind of problem. And it fuel squirts out the plug hole then it was hydrolocked with fuel bleeding past the carb(s).
#10
B
bertsmobile1
B
bertsmobile1
I will guess that you set the valve lash at TDC on the exhaust stroke and not on the compression stroke.
A common mistake we all make every now & then
So from scratch rotate the engine and watch the valves move with the spark plug removed
The lower ( inlet valve) should close ( rocker goes loose ) just after BDC then stay like that all the way till just before TDC when it opens a very tiny amount to decompress
The engine should then fire so both valves will be closed ( both rockers loose ) all the way to BDC when the Exhaust valve ( top one ) should open and stay open all the way to TDC where the inlet opens and then the exhaust closes .
The inlet remains open all the way to BDC then closes and you are back to the beginning.
The other trick that confuses people is you adjust the valve lash with the big nut and use the torx grub screw to lock the big nut .
If you are new to this it is a good idea to adjust the valves then run the engine for a few minutes ( messy ) then let it cool down stone cold and check them again .
Do not worry if you have to do them 4, 5 or 6 timed till you get the feel of it .
As for You tube videos forget most of the menstural clots you have been looking at.
I would bet that they are paying some computer hackers in India a lot of money so their trash videos come up first in any google search.
Remember every time you look at one of them some makes a cent or two
The only 2 I recommend are Taryl Fixes All & Donny Boy 87
Skip the first 30 seconds of Taryls videos if you do not find school boy humour funny
It is a ploy to make him more money.
You tube requires a viewer to be there for 15 seconds and if you time the preview followed by the animated title page than comes on before they start providing any information you wil see they all go better than 15 sec
From then on in they get credit for each block of time you stay there , usually in 30 sec incriments
None of them are there for your benefit
The brain dead ego maniacs are there to increase their self esteem and all the rest are there to make money and solicit free goods .
A common mistake we all make every now & then
So from scratch rotate the engine and watch the valves move with the spark plug removed
The lower ( inlet valve) should close ( rocker goes loose ) just after BDC then stay like that all the way till just before TDC when it opens a very tiny amount to decompress
The engine should then fire so both valves will be closed ( both rockers loose ) all the way to BDC when the Exhaust valve ( top one ) should open and stay open all the way to TDC where the inlet opens and then the exhaust closes .
The inlet remains open all the way to BDC then closes and you are back to the beginning.
The other trick that confuses people is you adjust the valve lash with the big nut and use the torx grub screw to lock the big nut .
If you are new to this it is a good idea to adjust the valves then run the engine for a few minutes ( messy ) then let it cool down stone cold and check them again .
Do not worry if you have to do them 4, 5 or 6 timed till you get the feel of it .
As for You tube videos forget most of the menstural clots you have been looking at.
I would bet that they are paying some computer hackers in India a lot of money so their trash videos come up first in any google search.
Remember every time you look at one of them some makes a cent or two
The only 2 I recommend are Taryl Fixes All & Donny Boy 87
Skip the first 30 seconds of Taryls videos if you do not find school boy humour funny
It is a ploy to make him more money.
You tube requires a viewer to be there for 15 seconds and if you time the preview followed by the animated title page than comes on before they start providing any information you wil see they all go better than 15 sec
From then on in they get credit for each block of time you stay there , usually in 30 sec incriments
None of them are there for your benefit
The brain dead ego maniacs are there to increase their self esteem and all the rest are there to make money and solicit free goods .
#11
B
Bertrrr
B
Bertrrr
I've been doing Mechanical work for 50 plus years and still reshearch things on Utube as well as on this site and am still learning some things - with the experience I have I can quickly weed out the BOZOs from the guys that actually know what they're talking about.
I can see where someone with less experience could get led down the wrong path.
This site has a lot of experience and input available and is nice to learn new trouble shooting ideas etc.
You can never get too focused on one path on a problem because you'll miss what's really going on I've learned not to rule out anything as I've been surprised often .
I can see where someone with less experience could get led down the wrong path.
This site has a lot of experience and input available and is nice to learn new trouble shooting ideas etc.
You can never get too focused on one path on a problem because you'll miss what's really going on I've learned not to rule out anything as I've been surprised often .
#12
Tiger Small Engine
Tiger Small Engine
The whole secret to learning on YouTube is patience, finding the right teachers, and lots of months and years of practice. The old timers and mentors are simply not there in person to help like they were years ago.I've been doing Mechanical work for 50 plus years and still reshearch things on Utube as well as on this site and am still learning some things - with the experience I have I can quickly weed out the BOZOs from the guys that actually know what they're talking about.
I can see where someone with less experience could get led down the wrong path.
This site has a lot of experience and input available and is nice to learn new trouble shooting ideas etc.
You can never get too focused on one path on a problem because you'll miss what's really going on I've learned not to rule out anything as I've been surprised often .
#13
B
bertsmobile1
B
bertsmobile1
Good point
Perhaps we should compile a list of You Tubers who are worth the effort of looking at.
However this might get a bit tricky
Steves Small Engine Saloon for instance has good reliable information apart from one thing
Never touch an engine if you have been or are drinking booze
I have been fetteling motorcycles ( and to a lesser exten cars ) that should have been sent to the scrap metal yard sinceI was around 14 so I know my way round engines
However actual mowers, apart from the locak Victa's was a different thing all together .
When bought the repair run 12 years ago ( my doen't time fly ) it was a very very steep learing curve.
The very first job that came throgh the door was a Husky with rusted on wheels so the ripped the axel out of the tranny case trying to remove it .
Thus I spent thousands of hours getting up to speed on You Tube
Most of what I saw was trash , often totally wrong, badly done and I just could not believe how many problems seemed to be because of the seat switch , which is of course very rarely the acual problem
Thus after a while I found some who seemed to know heir stuff and sat through their entire channel
Probably the most helpful was the Joe Pace set of 2 stroke Diagnostics and since following his recommendations I have replaced almost as many faulty fuel caps & tank vents as I have replaced diaphragms & gaskets that I would have never found .
Just a shame that he never did actual fix it videos
Perhaps we should compile a list of You Tubers who are worth the effort of looking at.
However this might get a bit tricky
Steves Small Engine Saloon for instance has good reliable information apart from one thing
Never touch an engine if you have been or are drinking booze
I have been fetteling motorcycles ( and to a lesser exten cars ) that should have been sent to the scrap metal yard sinceI was around 14 so I know my way round engines
However actual mowers, apart from the locak Victa's was a different thing all together .
When bought the repair run 12 years ago ( my doen't time fly ) it was a very very steep learing curve.
The very first job that came throgh the door was a Husky with rusted on wheels so the ripped the axel out of the tranny case trying to remove it .
Thus I spent thousands of hours getting up to speed on You Tube
Most of what I saw was trash , often totally wrong, badly done and I just could not believe how many problems seemed to be because of the seat switch , which is of course very rarely the acual problem
Thus after a while I found some who seemed to know heir stuff and sat through their entire channel
Probably the most helpful was the Joe Pace set of 2 stroke Diagnostics and since following his recommendations I have replaced almost as many faulty fuel caps & tank vents as I have replaced diaphragms & gaskets that I would have never found .
Just a shame that he never did actual fix it videos
#14
2ball
2ball
Ok, it may be fixed!
I adjusted the valves per the instructions here, it turned past the compression stroke by hand easier then before and it started up first try.
I will see if it stands the test of time.
Thank you for all of the help.
I almost feel like a real mechanic!
I adjusted the valves per the instructions here, it turned past the compression stroke by hand easier then before and it started up first try.
I will see if it stands the test of time.
Thank you for all of the help.
I almost feel like a real mechanic!
#15
R
Rivets
R
Rivets
Glad to hear it. Thank you for letting us know, most guys don’t have the time to do that.
#16
S
slomo
S
slomo
Fixed now but on a 20+ year old engine, might be worth it as the manual states, pull the head and decarbon the cylinder.
And don't forget the cooling fins and block.
And don't forget the cooling fins and block.
#18
B
Bertrrr
B
Bertrrr
In My opinion there is no such thing as Too Much Compression , never saw it in over 50 years on working on all sorts of machine
#19
F
Forest#2
F
Forest#2
And sometimes you might have to go back after it's run awhile and reset just the intake lash.
I've had to set some of them 31 series briggs at .002 to get a compression release due to worn/broken cam.
To get a quick test if setting the intake lash to minimum gets a compression release on that model engine I just add feller gauges taking the lash to minimum and test.
If you go to .001 lash with the feeler gauge in place and it still won't crank over you then know you are just burning daylight and whipping on a dead horse and have problems e3lsewhere that valve lash is not going to correct.
If you are going to work on that model OHV as mentioned previously a BRIGGS single cylinder SERVICE manual is a good thing.
I've had to set some of them 31 series briggs at .002 to get a compression release due to worn/broken cam.
To get a quick test if setting the intake lash to minimum gets a compression release on that model engine I just add feller gauges taking the lash to minimum and test.
If you go to .001 lash with the feeler gauge in place and it still won't crank over you then know you are just burning daylight and whipping on a dead horse and have problems e3lsewhere that valve lash is not going to correct.
If you are going to work on that model OHV as mentioned previously a BRIGGS single cylinder SERVICE manual is a good thing.
#20
C
CWatters
C
CWatters
On my B&S engine the valve adjustment was quite critical to getting the decompression cam to work. It wasn't working at .008-0.010 but was fine at 0.004.
Took me several goes to get them spot on because the locking seemed to effect the setting quite a bit. Have to recheck after locking.
If really sure they are spot on then most likely broken decompressor. I've not had to replace one but have heard its not too difficult.
Took me several goes to get them spot on because the locking seemed to effect the setting quite a bit. Have to recheck after locking.
If really sure they are spot on then most likely broken decompressor. I've not had to replace one but have heard its not too difficult.
#21
A
Albuck
A
Albuck
Once you've verified your valve settings, remove remove your air cleaner and put a piece of cardboard or the like over the intake tube. If she cranks and starts, it's your compression release. Very simple to check without going nuts.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#22
R
Richard Martin
R
Richard Martin
Make sure that one or both pushrods aren't bent too. Both of these pushrods are bent. It's just that one is bent more than the other (obviously).
#23
Travlitt
Travlitt
I too would like to know how you can have too much compression.In My opinion there is no such thing as Too Much Compression , never saw it in over 50 years on working on all sorts of machine
#24
L
LMPPLUS
L
LMPPLUS
Once you get valves set right, intake .003-.005 and exhaust .005-.007 try it if still to much you may have a bad decompression release requiring a camshaft replacement.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#25
Dreaded
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.
Dreaded
I service a lot of mowers and have had to replace several cams. If it had no valve gap meaning the valves were being held open, it should have turned over easy. The less gap you have the easier it should turn over. That being said which from your description it sounds like at some point someone before you got the engine, adjusted the valves real tight to make it start easier. Because cam wear makes the gap larger the only ways they could be too tight is someone adjusted them too tight, the push rod guides are worn, or the cam bearings/bushings have caused the case to wear and, in some way, caused the cam to be positioned closer to the head which is most unlikely. One other thing to check before tearing engine down is the push rod guides, if the (plastic in some cases) guide is worn it can allow the push rod to move out of position and tighten the valves. I have seen this too but, in most cases, it will come out from in under the lifter.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.
#26
Dreaded
So there is a lot more to this than most people can achieve due to mechanical ability. I suggesttaking mower to someone who has experience with reworking small engines.
Dreaded
There is another problem you could have that you need to check if your tear the engine down and that is the valves themselves to insure they are not sticking and slide freely. To do this you need to remove the valve springs. the valves should not have to be pushed in and out they should fall using only their own weight. If you have to push them then carbon build up in the valve guide has to be cleaned out.I service a lot of mowers and have had to replace several cams. If it had no valve gap meaning the valves were being held open, it should have turned over easy. The less gap you have the easier it should turn over. That being said which from your description it sounds like at some point someone before you got the engine, adjusted the valves real tight to make it start easier. Because cam wear makes the gap larger the only ways they could be too tight is someone adjusted them too tight, the push rod guides are worn, or the cam bearings/bushings have caused the case to wear and, in some way, caused the cam to be positioned closer to the head which is most unlikely. One other thing to check before tearing engine down is the push rod guides, if the (plastic in some cases) guide is worn it can allow the push rod to move out of position and tighten the valves. I have seen this too but, in most cases, it will come out from in under the lifter.
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.
So there is a lot more to this than most people can achieve due to mechanical ability. I suggesttaking mower to someone who has experience with reworking small engines.
#27
G
Gord Baker
G
Gord Baker
It would appear that you have a Failure of the Automatic Compression Release (ACR) mechanism.
Simply put, it releases some compression during startup. The only cure is to replace the Camshaft to which this is attached to. First, be sure you can obtain a new one From B&S. Aftermarket ones can fail quickly.
There are many tutorials on changing the Cam and bottom Crankshaft seal. I admire your learning on Utube.
Just don't watch the ones where someone is doing a carb over grass!
Simply put, it releases some compression during startup. The only cure is to replace the Camshaft to which this is attached to. First, be sure you can obtain a new one From B&S. Aftermarket ones can fail quickly.
There are many tutorials on changing the Cam and bottom Crankshaft seal. I admire your learning on Utube.
Just don't watch the ones where someone is doing a carb over grass!
#28
K
kjonxx
K
kjonxx
When one valve is closed (down) then set the up one to .005. Repeat for the other. Never had a problem. Also you mentioned alot of oil under valve cover could mean overfilled.
#29
Michael72
Michael72
If valves are set correctly and you still have high compression it's your compression release on the cam shaft.. with plug out and justbefore TDC your exhaust vale should bump open a tad to allow compression out for fire up.. if it's a briggs 17.5 intek they are famous for cam issues.. always be sure to check you don't have a snagged belt on transmission or deck too..17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#30
justin@justintime
justin@justintime
you got some wrong info too much clearance on your exhaust valve is what's causing "too much compression" and it's not that it's too much it's just not hitting the compression release set intake (aluminum push rod) to .004" that inches. set exhaust (steel push rod) to .006" INCHES......oil in the cover is expected. if your problem persists, the camshaft's decompression mechanism is probably broken. after you adjust the valves again roll the engine over by hand and you should see a "bump" on the exhaust valve as you come up on the compression stroke.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#31
M
mmoffitt
M
mmoffitt
From my observation and experience...First things first like the nice policeman says ""License and Registration" first... that Equates to """Make Model and serial number""" so these "Fine, Gentle people",I use the term "loosely"! Can do their best thir best to help you from the get go!!!
Thanks for everyones help in the past please all be well and safe out there!
Thanks for everyones help in the past please all be well and safe out there!
#32
J
Johner
J
Johner
Good info, knew they were there to make money, the timing of the skit I did not know, very informative and yes Taryl is very good.I will guess that you set the valve lash at TDC on the exhaust stroke and not on the compression stroke.
A common mistake we all make every now & then
So from scratch rotate the engine and watch the valves move with the spark plug removed
The lower ( inlet valve) should close ( rocker goes loose ) just after BDC then stay like that all the way till just before TDC when it opens a very tiny amount to decompress
The engine should then fire so both valves will be closed ( both rockers loose ) all the way to BDC when the Exhaust valve ( top one ) should open and stay open all the way to TDC where the inlet opens and then the exhaust closes .
The inlet remains open all the way to BDC then closes and you are back to the beginning.
The other trick that confuses people is you adjust the valve lash with the big nut and use the torx grub screw to lock the big nut .
If you are new to this it is a good idea to adjust the valves then run the engine for a few minutes ( messy ) then let it cool down stone cold and check them again .
Do not worry if you have to do them 4, 5 or 6 timed till you get the feel of it .
As for You tube videos forget most of the menstural clots you have been looking at.
I would bet that they are paying some computer hackers in India a lot of money so their trash videos come up first in any google search.
Remember every time you look at one of them some makes a cent or two
The only 2 I recommend are Taryl Fixes All & Donny Boy 87
Skip the first 30 seconds of Taryls videos if you do not find school boy humour funny
It is a ploy to make him more money.
You tube requires a viewer to be there for 15 seconds and if you time the preview followed by the animated title page than comes on before they start providing any information you wil see they all go better than 15 sec
From then on in they get credit for each block of time you stay there , usually in 30 sec incriments
None of them are there for your benefit
The brain dead ego maniacs are there to increase their self esteem and all the rest are there to make money and solicit free goods .
#33
D
DHook
D
DHook
I enjoy Taryl's videos but could do with less of the off-topic theatrics. Just the facts, mam. I've watched quite a few of them and am going to attempt a fluid change on a hydro-static tuff-torq transmission soon on a Husqvarna mower I bought for $25.
Re: the valve adjustment; do you do that on a warm or cold engine the first time? I know you should run it after the adjustment and check again but the first adjustment, warm or cold engine?
Re: the valve adjustment; do you do that on a warm or cold engine the first time? I know you should run it after the adjustment and check again but the first adjustment, warm or cold engine?
#35
E
Earthquake Landscaping
E
Earthquake Landscaping
Personally, as other posters have mentioned.... I agree! There's no such thing as too much compression!!
Let's look at that from a not too technical viewpoint....
"ACR" .. AKA.. Automatic Compression Release. Well, What does that actually do? AFAIK, the compression release is there so that you can just try to start a motor without having to make sure that you have tweaked the engine to a point where you will rotate it 270 degrees before it hits another compression stroke. Basically, if you start from TDC, on the combustion cycle, by the time that the engine gets to the next compression stroke, it should be rotating fast enough to overcome the compression, and continue rotating with enough R.P.M. to provide sufficient vacuum at the Carb, so as to properly atomize fuel for combustion. At that point, a "ACR", isn't necessary for starting.
That being said, I'm not going to debate that the ACR system needs to be correctly set, for optimal operating. That's just over my head.
Valve lash settings don't really have a significant effect on overall compression ratios. When you're turning an engine over by hand, or with a starter motor, there's plenty of time, when the valves are open, to allow sufficient air into the cylinder (s), to have air ( mixture) available to compress for combustion. The throttle should be wide open for a compression test. Too tight valve settings, would result in ... low compression ( leakage ), burnt valves, ( if it even ran), and is actually an unlikely scenario, ( unless improperly set). Loose valve settings would be noisy, and result in lowered power output, as the lift, overlap, and duration become less than optimal. Set tight ( as far as tolerances is concerned), is like having a high performance cam shaft. Set loose, ( at the high end of the spec), is like having a smogger cam..
"Hydrolock".. Hydro lock doesn't make it difficult to turn over an engine... it makes it pretty much impossible! Fuel, like other fluids ( water, oil, etc.) , are, for all practicable purposes, non- compressible. A Hydro locked engine wouldn't just be stiff to turn, it would be impossible to turn.
Also interesting was the observation by the OP, that, with the plug out, it was easier to turn.. Hmmmmm.. It shouldn't have just been easier to turn, it should have been almost effortless to turn over.. There should have been very little difference of the force needed to turn it over anywhere in the 4 strokes,, If turning it over without a plug in it wasn't easy - peasy just like butter.. then there's a reason to look further into the internal mechanics of the engine.
Let's look at that from a not too technical viewpoint....
"ACR" .. AKA.. Automatic Compression Release. Well, What does that actually do? AFAIK, the compression release is there so that you can just try to start a motor without having to make sure that you have tweaked the engine to a point where you will rotate it 270 degrees before it hits another compression stroke. Basically, if you start from TDC, on the combustion cycle, by the time that the engine gets to the next compression stroke, it should be rotating fast enough to overcome the compression, and continue rotating with enough R.P.M. to provide sufficient vacuum at the Carb, so as to properly atomize fuel for combustion. At that point, a "ACR", isn't necessary for starting.
That being said, I'm not going to debate that the ACR system needs to be correctly set, for optimal operating. That's just over my head.
Valve lash settings don't really have a significant effect on overall compression ratios. When you're turning an engine over by hand, or with a starter motor, there's plenty of time, when the valves are open, to allow sufficient air into the cylinder (s), to have air ( mixture) available to compress for combustion. The throttle should be wide open for a compression test. Too tight valve settings, would result in ... low compression ( leakage ), burnt valves, ( if it even ran), and is actually an unlikely scenario, ( unless improperly set). Loose valve settings would be noisy, and result in lowered power output, as the lift, overlap, and duration become less than optimal. Set tight ( as far as tolerances is concerned), is like having a high performance cam shaft. Set loose, ( at the high end of the spec), is like having a smogger cam..
"Hydrolock".. Hydro lock doesn't make it difficult to turn over an engine... it makes it pretty much impossible! Fuel, like other fluids ( water, oil, etc.) , are, for all practicable purposes, non- compressible. A Hydro locked engine wouldn't just be stiff to turn, it would be impossible to turn.
Also interesting was the observation by the OP, that, with the plug out, it was easier to turn.. Hmmmmm.. It shouldn't have just been easier to turn, it should have been almost effortless to turn over.. There should have been very little difference of the force needed to turn it over anywhere in the 4 strokes,, If turning it over without a plug in it wasn't easy - peasy just like butter.. then there's a reason to look further into the internal mechanics of the engine.
#36
woodstover
woodstover
Always adjust valves on a cold engine.I enjoy Taryl's videos but could do with less of the off-topic theatrics. Just the facts, mam. I've watched quite a few of them and am going to attempt a fluid change on a hydro-static tuff-torq transmission soon on a Husqvarna mower I bought for $25.
Re: the valve adjustment; do you do that on a warm or cold engine the first time? I know you should run it after the adjustment and check again but the first adjustment, warm or cold engine?
#37
C
cleverlever
C
cleverlever
I had the same problem and fixed it by loosening the valve lash. Put a compression gauge in it and watched as I loosened the lash. Didn't have to add to much lash to get the compression up. Started really easy. I have had the worst problems with compression release on the Kawasaki's.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#38
E
Earthquake Landscaping
E
Earthquake Landscaping
"of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running."
Sometimes, the devil is in the details....
So.. It only started 2 times on the "first try".. Did it take 3 more tries to get it started, but it did start? That comment / observation isn't much information for clarity..
If having the miniscule amount of extra grunt from the battery charger being connected when starting makes a difference.. then the battery is suspect. Realistically, a battery is designed to put out a maximum output for starting, and then slowly re-charge from the electrical system. A 30 amp hour battery takes 3 hours to recharge from flat with a 10 amp hour charge. What little the battery charger puts out, compared to the electrical demands of the starter motor's use is almost negligible. The only exception would be a charger with a booster function.
Voltage is a "thing" for batteries... so, however, is cranking amps. More specifically, CCA ( Cold Cranking Amps).. These are the amps that spin the engine. Sim[ply having enough voltage, doesn't necessarily spin the engine hard enough to start. IMHO, 350 cranking amps is a minimum, especially in cold weather.
Either load test the battery, or try starting it with jumper cables and a fully charged automotive battery, to eliminate the battery's lack of cranking amps as the root cause of the problem. If it stats with a jump.. look at a new battery. Just because it shows voltage isn't necessarily meaning that it has the necessary amps.
12.8 volts ( resting charge) .. is actually a bit high .. I usually see 12.6 .. to 12.7.. And, 14.6 on charge... I've never seen 16 volts as a charging voltage. To me, that would indicate a battery issue. Once started, the charging system should quickly replenish the drain in the battery from starting, and return to th e 12.6 to 13.0 volt range, as the battery approaches full charge.
Sometimes, the devil is in the details....
So.. It only started 2 times on the "first try".. Did it take 3 more tries to get it started, but it did start? That comment / observation isn't much information for clarity..
If having the miniscule amount of extra grunt from the battery charger being connected when starting makes a difference.. then the battery is suspect. Realistically, a battery is designed to put out a maximum output for starting, and then slowly re-charge from the electrical system. A 30 amp hour battery takes 3 hours to recharge from flat with a 10 amp hour charge. What little the battery charger puts out, compared to the electrical demands of the starter motor's use is almost negligible. The only exception would be a charger with a booster function.
Voltage is a "thing" for batteries... so, however, is cranking amps. More specifically, CCA ( Cold Cranking Amps).. These are the amps that spin the engine. Sim[ply having enough voltage, doesn't necessarily spin the engine hard enough to start. IMHO, 350 cranking amps is a minimum, especially in cold weather.
Either load test the battery, or try starting it with jumper cables and a fully charged automotive battery, to eliminate the battery's lack of cranking amps as the root cause of the problem. If it stats with a jump.. look at a new battery. Just because it shows voltage isn't necessarily meaning that it has the necessary amps.
12.8 volts ( resting charge) .. is actually a bit high .. I usually see 12.6 .. to 12.7.. And, 14.6 on charge... I've never seen 16 volts as a charging voltage. To me, that would indicate a battery issue. Once started, the charging system should quickly replenish the drain in the battery from starting, and return to th e 12.6 to 13.0 volt range, as the battery approaches full charge.
#39
C
Chrisgixer2
C
Chrisgixer2
Suggest either
hydro locking ( pull the plug as said, turn it over, re fit plug try again. But you know all that )
or oil too thick. Is it worse when cold ?
hydro locking ( pull the plug as said, turn it over, re fit plug try again. But you know all that )
or oil too thick. Is it worse when cold ?
#40
T
TobyU
Don't get me wrong, I love Briggs & Stratton engines, some of them. I just call out what is crap.
I don't know why people want to insist on applying normal valve train and car valve train to these engines.
Don't do it!
Don't do the set one valve while the other valve is closed and all that crap.
It's not a car!
It's a low performance little turd mower engine so do it the way the manufacturer designed it to be set and designed it to work.
It is very simple.
Turn the engine over by hand until you get to top dead center on the compression stroke and then turn it until the Piston goes down at least one half inch past top dead center.
Now in reality, like I've told people for years, you can go a lot further than that and you can actually go all the way until almost bottom dead center until the exhaust valve starts to open so you have a lot of leeway there but the point is you need to get past top dead center!
So get the Piston pass top dead center and down an inch or an inch and a half and you're good to go setting both valves.
Now, I also don't know why people get into setting them at different than Factory spec clearances or making them more loose like they're giving some extra margin of safety.
I understand that unexhaust valves or any valve that could burn which is typically an exhaust valve, being closed longer is better so in this case more clearance is better but that's just not necessary!!
Set the darn things to watch the book calls for!
They already give you .002 a variance from Titus to loosest for each clearance so if you feel the need to go to the high side that's fine but don't go .008. when the spec is 005-007.
I know in reality it's not that big of a deal but come on people...
On the intake you should go on the tight side to get as much out of the ACR as you can.
The reason you don't have to go any larger even on the exhaust is because these things do not wear tight like a car or like many other engines.
You would think they would as the valve margin on the seat erodes and the valve stem tip effectively gets longer but that's just not how these work.
What happens 10.5 times out of 10 is the rocker arm tip and the valve stem cap and probably the push rod tip also or at least the rocker arm pocket it sits in wear away a little bit of metal so the clearance gets greater which means looser.
EVERY time you pull one of these engines apart that's been together for a while you will find these clearances at .010 to .016 etc.
Now that I'm off my soapbox.. the way to see if your ACR on the camshaft is busted is to adjust the intake valve correctly or just set it to zero lash where it's touching for test purposes and then turn the engine over by hand or spin it with the starter.
You will see the intake valve open and then close and immediately after it closes it will bump open for just a split second.
We call it the bump.
If it doesn't noticeably bump open slightly then your ACR is busted.
There is a workaround for this though and that's to take your air filter off and turn the engine backwards counterclockwise with your hands until it gets to the hard spot again. Then hold your hand over the air filter intake so you block off all the air. You should probably also have the choke closed when you do this...
This will make the engine easier to spin over because it won't have as much air inside of it to compress so it won't be compressing so hard.
I have been able to get everyone of these to start just fine this way and then of course they will mow fine it's just starting them that's hard.
It's not ideal because you do have a couple of little pieces of metal in a spring laying there and your base plate but oh well.
I replaced the number of these and I started out using all Briggs & Stratton brand parts and then I migrated over to the off-brands on eBay and Amazon and did three or four of them without any problems.
But then, last year I had major problems with one that failed in just a couple of months with only five or six mows.
It didn't fail the way the ACR fails but the cheap metal press on lobes and the splines on the shaft just stripped off and it got out of camshaft timing for the valves.
This made me afraid to use any more of them and if you read the reviews they are absolutely horrendous..
So I replaced it with a Briggs & Stratton with the new upgraded part number and so far it's been fine.
T
TobyU
It's very possible because the ACR on these Briggs & Stratton engines is an absolute joke! They should have fixed the problem long ago but Briggs basically refuses to fix anything of their inferior quality designs.I am pretty sure I understand how to adjust the valves. I am good with that.
So after watching a couple videos, I am wondering if the compression release and cam shaft are not working properly.
when starting the engine it gets caught up on the compression stroke. I need to double check, but I think the bottom valve does not move like the top valve.
The engine is almost 20 years old and I got it used.
Could I have a cam shaft/ compression release issue? How would I know for sure?
Don't get me wrong, I love Briggs & Stratton engines, some of them. I just call out what is crap.
I don't know why people want to insist on applying normal valve train and car valve train to these engines.
Don't do it!
Don't do the set one valve while the other valve is closed and all that crap.
It's not a car!
It's a low performance little turd mower engine so do it the way the manufacturer designed it to be set and designed it to work.
It is very simple.
Turn the engine over by hand until you get to top dead center on the compression stroke and then turn it until the Piston goes down at least one half inch past top dead center.
Now in reality, like I've told people for years, you can go a lot further than that and you can actually go all the way until almost bottom dead center until the exhaust valve starts to open so you have a lot of leeway there but the point is you need to get past top dead center!
So get the Piston pass top dead center and down an inch or an inch and a half and you're good to go setting both valves.
Now, I also don't know why people get into setting them at different than Factory spec clearances or making them more loose like they're giving some extra margin of safety.
I understand that unexhaust valves or any valve that could burn which is typically an exhaust valve, being closed longer is better so in this case more clearance is better but that's just not necessary!!
Set the darn things to watch the book calls for!
They already give you .002 a variance from Titus to loosest for each clearance so if you feel the need to go to the high side that's fine but don't go .008. when the spec is 005-007.
I know in reality it's not that big of a deal but come on people...
On the intake you should go on the tight side to get as much out of the ACR as you can.
The reason you don't have to go any larger even on the exhaust is because these things do not wear tight like a car or like many other engines.
You would think they would as the valve margin on the seat erodes and the valve stem tip effectively gets longer but that's just not how these work.
What happens 10.5 times out of 10 is the rocker arm tip and the valve stem cap and probably the push rod tip also or at least the rocker arm pocket it sits in wear away a little bit of metal so the clearance gets greater which means looser.
EVERY time you pull one of these engines apart that's been together for a while you will find these clearances at .010 to .016 etc.
Now that I'm off my soapbox.. the way to see if your ACR on the camshaft is busted is to adjust the intake valve correctly or just set it to zero lash where it's touching for test purposes and then turn the engine over by hand or spin it with the starter.
You will see the intake valve open and then close and immediately after it closes it will bump open for just a split second.
We call it the bump.
If it doesn't noticeably bump open slightly then your ACR is busted.
There is a workaround for this though and that's to take your air filter off and turn the engine backwards counterclockwise with your hands until it gets to the hard spot again. Then hold your hand over the air filter intake so you block off all the air. You should probably also have the choke closed when you do this...
This will make the engine easier to spin over because it won't have as much air inside of it to compress so it won't be compressing so hard.
I have been able to get everyone of these to start just fine this way and then of course they will mow fine it's just starting them that's hard.
It's not ideal because you do have a couple of little pieces of metal in a spring laying there and your base plate but oh well.
I replaced the number of these and I started out using all Briggs & Stratton brand parts and then I migrated over to the off-brands on eBay and Amazon and did three or four of them without any problems.
But then, last year I had major problems with one that failed in just a couple of months with only five or six mows.
It didn't fail the way the ACR fails but the cheap metal press on lobes and the splines on the shaft just stripped off and it got out of camshaft timing for the valves.
This made me afraid to use any more of them and if you read the reviews they are absolutely horrendous..
So I replaced it with a Briggs & Stratton with the new upgraded part number and so far it's been fine.
#41
C
cary09
C
cary09
FWIW, I found this answer out in left field... Had similar compression/starting issues. Also, needed an oil change. As luck would have it, a nice shiny 1/4" piece (the pivot pin from the ACR) dripped out in the oil. Question solved.
#42
G
groundsman1
G
groundsman1
Hi. Is it a Briggs & Stratton
17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#43
G
groundsman1
Eddie.
G
groundsman1
Hi . If it is a Briggs & Stratton INTEK engine you will most probably find that the decompression mechanism fitted to the camshaft has broken. They are prone to this. What this mechanism does is it lifts the exhaust valve very slightly to reduce the compression on starting. When the engine starts the mechanism drops out and the engine runs normal. If this device fails there is too much compression for the starter to turn it over. I hope this helps17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
Eddie.
#44
S
smallenginesmd
MD Small Engines (retired) Ontario , Canada
S
smallenginesmd
Most likely the compression release on the cam is broken. If engine turns over easy with the plug out then it's the CR. Common on OHV single cyl B&S. To verify turn the engine over(with the plug in) by hand past the compression stroke and then attempt to key start. If it starts or spins freely to the next compression stroke you know it's the CR. Remove the engine, remove the oil sump pan & remove the cam. The release spring will be broken. New cam comes with the release assembly. Don't attempt to repair the spring. It can be a bit expensive with the new cam, gasket(s), oil etc. Might be cheaper to look for another motor.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
MD Small Engines (retired) Ontario , Canada
#45
F
Forest#2
F
Forest#2
Breaking news:
On page 2 post #14 he indicates that the proper valve adjustment fixed his engine.
On page 2 post #14 he indicates that the proper valve adjustment fixed his engine.
#46
E
Earthquake Landscaping
E
Earthquake Landscaping
But... But... But.. It was so much more fun to continue on as if he hadn't...
Ain't that just ( . ) ( . )
Ain't that just ( . ) ( . )
#47
P
powermax
P
powermax
Does no one have a B&S shop manual?
Manual says remove plug bring piston to TDC. Insert screw driver, turn PAST tdc 1/4 inch then adjust.
Solved my starting problem.
Manual says remove plug bring piston to TDC. Insert screw driver, turn PAST tdc 1/4 inch then adjust.
Solved my starting problem.
#48
2ball
2ball
Good Stuff.
I have had 3 unassisted starts since properly adjusting the valves and I am going to call it fixed.
I may have a ACR issue, but maybe this worn old engine can start with full compression when everything else is perfect( valves and battery etc).
I may have a battery issue. I let my battery drain all the way down 2 years ago when it was brand new when I forgot to turn the key off and it sat like that for a week, and I tipped it over once and and a tea spoon or so of the acid spilled out.
So for now, I'm calling it fixed. It runs and cuts grass.
I have had 3 unassisted starts since properly adjusting the valves and I am going to call it fixed.
I may have a ACR issue, but maybe this worn old engine can start with full compression when everything else is perfect( valves and battery etc).
I may have a battery issue. I let my battery drain all the way down 2 years ago when it was brand new when I forgot to turn the key off and it sat like that for a week, and I tipped it over once and and a tea spoon or so of the acid spilled out.
So for now, I'm calling it fixed. It runs and cuts grass.
#49
A
Alton R
A
Alton R
You
I know some of these engines can have a broken camshaft pressure release. But in that case it's hard to turn over but you can find still turn the engine over with a socket rinch.
Are you sure something is not in the cylinder. You need to remove the spark plugs and see if it will turn over. If it won't turn over with out plugs in it you have a mech
Sure that it's compression or is something broken in the engine.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
I know some of these engines can have a broken camshaft pressure release. But in that case it's hard to turn over but you can find still turn the engine over with a socket rinch.
Are you sure something is not in the cylinder. You need to remove the spark plugs and see if it will turn over. If it won't turn over with out plugs in it you have a mech
Sounds like you have a mechanical problem to me. Remove the plugs then see if it's still hard to turn over.17.5hp IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#50
mpqualdie
mpqualdie
If it's a Briggs and Stratton the camshaft most likely broke. I have a 21hp and a 17hp the same thing happened to, it's a common issue with them. There's a nub on the cam that opens the intake valve a little to relieve the compression so the starter can spin the motor. Once it starts the centrifugal force will fold the nub out of the way. If your mechanically inclined, it's an easy fix. Remove the motor, drain oil, flip it over and remove the bottom cover. Replace camshaft, put it back together (new seal too) adjust valves. Also, make sure you meticulously clean all of the debris out of the inside of the motor before re assembling.
#51
C
CJSNIDER
C
CJSNIDER
Try starting a Briggs with a worn camshaft, or a two-stroke with carbon build-up on the head and piston, and you will find out first-hand about compression.In My opinion there is no such thing as Too Much Compression , never saw it in over 50 years on working on all sorts of machine
#52
C
CJSNIDER
C
CJSNIDER
When the valve face and valve seats in the head wear, the clearance is reduced.I service a lot of mowers and have had to replace several cams. If it had no valve gap meaning the valves were being held open, it should have turned over easy. The less gap you have the easier it should turn over. That being said which from your description it sounds like at some point someone before you got the engine, adjusted the valves real tight to make it start easier. Because cam wear makes the gap larger the only ways they could be too tight is someone adjusted them too tight, the push rod guides are worn, or the cam bearings/bushings have caused the case to wear and, in some way, caused the cam to be positioned closer to the head which is most unlikely. One other thing to check before tearing engine down is the push rod guides, if the (plastic in some cases) guide is worn it can allow the push rod to move out of position and tighten the valves. I have seen this too but, in most cases, it will come out from in under the lifter.
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.
#54
Hammermechanicman
Hammermechanicman
What's a shop manual?Does no one have a B&S shop manual?
Manual says remove plug bring piston to TDC. Insert screw driver, turn PAST tdc 1/4 inch then adjust.
Solved my starting problem.
#55
E
Earthquake Landscaping
E
Earthquake Landscaping
A "Shop Manual", is what you put under your beer, so that you don't get white rings on the coffee table.What's a shop manual?
#56
Hammermechanicman
Hammermechanicman
Good to know!A "Shop Manual", is what you put under your beer, so that you don't get white rings on the coffee table.
#58
2ball
2ball
That is my exact engine and my exact issue, but If the mower keeps starting, I will keep pushing that fix back.It has nothing to do with the valves.
#59
B
BillS2019
B
BillS2019
My Kohler has the same issue. Been that way for 5-6 years and I will just keep rolling it off compression by hand.
#60
2ball
2ball
Just reflecting on this. Three years ago I got the mower with a blown engine free. I replaced the engine with a used engine. A new engine was somewhere in the $500 range. 3 years have passed and if I replace the cam shaft, I will be in at least $350 on this used engine. I probably made the wrong decision not buying a new engine.
#61
flyhalhl@gmail.co.
flyhalhl@gmail.co.
Briggs & Stratton
17.5hp Intek IC
model 31C707-0154-E1
I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.
I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.
The motor was even harder to turn then before. almost impossible to turn it by hand.
What do I need to look at next?
#62
flyhalhl@gmail.co.
flyhalhl@gmail.co.
About twice too much clearance. 3 to 4 thousanths more normal for these overhead valve engines. Valve adj controls the compression release. So valves open slightly before piston at TDC (max compression). Valves to loose (big gap) they release to much of compression so cylinder will not fire. And valves too tight, compression so high that starter does not have enough torque to rotate piston thru TDC/full compression.
These overhead valves are notorious for valve wear and not opening the valve to reduce compression when starting. When engine is running, piston moving too fast to reduce compression much.
These overhead valves are notorious for valve wear and not opening the valve to reduce compression when starting. When engine is running, piston moving too fast to reduce compression much.