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Briggs 500 Series - Interesting troubleshooting case for the pros. help needed.
#1
motormonkey
motormonkey
Hello!
First of all I want to say this place is great. been reading for a long time but just signed up.
Ok so... Here's a little story on the background of the issue...
I was asked to fix a lawnmower with a B&S 500 Series (Model # 10T502) on it.
When trying to start it by pulling the recoil it wouldn't even fire and there was a knocking sound in the crankcase.
I removed the fuel tank and drained the oil. I removed the blade and took the motor off the frame and set it up on a motor stand to work on it.
upon removing the head I found a stuck intake valve, lots of carbon on the piston head and on the valves and head but the cylinder walls were in awesome shape actually.
I then split the crankcase because there was no way to un-stick the valve and I needed to work the valves over, clean them up etc.
After removing the camshaft, and removing the valve lifters I could access the bottom of the stuck valve with a very large screwdriver and pry it straight up after removing the valve spring retainer.
I pried the valve up and finally was able to remove it and clean and sand the valves, valve seats and I cleaned the valve stems very lightly with very fine grit sandpaper.
Unfortunately I didn't have a valve lapping tool or compound to to it with so I sanded the valves and valve seats with extra fine sandpaper(500 - 1000 grit) until they seated beautifully. cleaned down the valve guides etc. the valves were working beautifully with just a SLIGHT play in the valves ( and rightly so due to the age, wear and lack of oil changes in the mower).
after that I reassembled the valves, put the springs and retainers back on, the valve lifters in and the Camshaft back in and set my timing marks dead on with cam and crank. (doubled checked my timing by the way the valves moved at TDC on exhaust stroke.)
Then I put a new head gasket on, a little Red Grease (High-Temp) to help protect the head gasket from the heat and reassembled the mower.
I did the old "thumb-Check" for compression covering the spark plug hole with my thumb and it had normal compression. (obviously my thumb can't read psi but you get a feel for it)
put the plug back in, Filled the Oil to correct level, fresh fuel etc,.
primed the carb with 3 squirts from it's PulsaJet carb and it started right up on the 2nd Pull.
It purred like a kitten, I mowed with it for a little bit... then I let go of the bail handle to kill it then I immediately started it back up with 1 pull.
then... I shut it off and came back to it about 15 - 20 minutes later I came back... and.... it wouldn't start.... it had that knock sound of the Camshaft turning but not able to lift 1 or more valves...
I proceeded to remove the valve spring access cover. (took the plug out) and had someone pull the mower rope.. and sure enough.. the valves were not moving.... ( I could move the exhaust valve with a screwdriver no problem... but the intake valve is apparently stuck again.
SO.. I am guessing.. the Camshaft is bent from before.
the cam would about have to be bent for it to be able to turn over if the valves aren't moving.. other wise it would be seized if the cam was straight wouldn't it?
Can someone please give me some insight into why this would stick like this again, so quick, after purring like a kitten. I know I have to tear it down again but some advice.. or moral support would be wonderful.
Many Thanks in Advance.
-
First of all I want to say this place is great. been reading for a long time but just signed up.
Ok so... Here's a little story on the background of the issue...
I was asked to fix a lawnmower with a B&S 500 Series (Model # 10T502) on it.
When trying to start it by pulling the recoil it wouldn't even fire and there was a knocking sound in the crankcase.
I removed the fuel tank and drained the oil. I removed the blade and took the motor off the frame and set it up on a motor stand to work on it.
upon removing the head I found a stuck intake valve, lots of carbon on the piston head and on the valves and head but the cylinder walls were in awesome shape actually.
I then split the crankcase because there was no way to un-stick the valve and I needed to work the valves over, clean them up etc.
After removing the camshaft, and removing the valve lifters I could access the bottom of the stuck valve with a very large screwdriver and pry it straight up after removing the valve spring retainer.
I pried the valve up and finally was able to remove it and clean and sand the valves, valve seats and I cleaned the valve stems very lightly with very fine grit sandpaper.
Unfortunately I didn't have a valve lapping tool or compound to to it with so I sanded the valves and valve seats with extra fine sandpaper(500 - 1000 grit) until they seated beautifully. cleaned down the valve guides etc. the valves were working beautifully with just a SLIGHT play in the valves ( and rightly so due to the age, wear and lack of oil changes in the mower).
after that I reassembled the valves, put the springs and retainers back on, the valve lifters in and the Camshaft back in and set my timing marks dead on with cam and crank. (doubled checked my timing by the way the valves moved at TDC on exhaust stroke.)
Then I put a new head gasket on, a little Red Grease (High-Temp) to help protect the head gasket from the heat and reassembled the mower.
I did the old "thumb-Check" for compression covering the spark plug hole with my thumb and it had normal compression. (obviously my thumb can't read psi but you get a feel for it)
put the plug back in, Filled the Oil to correct level, fresh fuel etc,.
primed the carb with 3 squirts from it's PulsaJet carb and it started right up on the 2nd Pull.
It purred like a kitten, I mowed with it for a little bit... then I let go of the bail handle to kill it then I immediately started it back up with 1 pull.
then... I shut it off and came back to it about 15 - 20 minutes later I came back... and.... it wouldn't start.... it had that knock sound of the Camshaft turning but not able to lift 1 or more valves...
I proceeded to remove the valve spring access cover. (took the plug out) and had someone pull the mower rope.. and sure enough.. the valves were not moving.... ( I could move the exhaust valve with a screwdriver no problem... but the intake valve is apparently stuck again.
SO.. I am guessing.. the Camshaft is bent from before.
the cam would about have to be bent for it to be able to turn over if the valves aren't moving.. other wise it would be seized if the cam was straight wouldn't it?
Can someone please give me some insight into why this would stick like this again, so quick, after purring like a kitten. I know I have to tear it down again but some advice.. or moral support would be wonderful.
Many Thanks in Advance.
-
#2
reynoldston
reynoldston
When you install a valve you want about .003 between the valve stem and valve guide. You need some oil clearance.
#3
motormonkey
Hello Reynoldston,
Then it sounds like in that regard we are OK because there is some oil clearance.
motormonkey
When you install a valve you want about .003 between the valve stem and valve guide. You need some oil clearance.
Hello Reynoldston,
Then it sounds like in that regard we are OK because there is some oil clearance.
#4
M
motoman
M
motoman
motor, Not a pro, just a tinkerer...Try some checks. Did you take the lifters out and look? Lobe lift is the difference between a mike meas on the "base circle" and the lift . Compare the cams for wear and check the lift spec. My Intek had ground down its ex valve so that there was only 1/8 " lift and it still ran. (That cylinder finally went away). Stuck valves seem a bit of a mystery. Plane guys and some tractor guys see carbon (coke) buid-up as the culprit. This often happens on a very hot engine being shut down without reaching a reasonable temp. But in those cases bent pushrods are seen , or bent push rods drop out. I do not rebuild ac engines, but .003 guide oil clearance seems excessive. This may allow "cocking" of the stem in guide. You have not mentioned a guide seal. As you know these are used to control oil into the combustion chamber. I am surprised my Intake has a seal on the (? I think) ex valve as this is where the heat is generated. So with a seal the Briggs guys don't seem to want .003" oil film. I would carefully check all valve gear for cracks and wear and replace the springs. Hope some of this blather can help solve the problem or motivate the great forum knowers to respond, BTW removing and reinstalling valve guides did not work for me and BS does not sell guides (for my Intek , anyway), only assembled heads. My guess is that these engines fail mostly from valve mechanism problems if they are not fried from lack of oil/overwork. (As in using a 3 bagger on a hill with damp grass in 85F weather).:laughing:
#5
reynoldston
I wouldn't think .003 is excessive at all. But I am thinking a car engine and don't know what the Briggs engine calls for. I would say go to the service manual and see what it dose call for because I was just guessing on that number. Oil dose take up space and you do need this space to lubricate the valve stems and without proper lube they will stick when they get hot.
reynoldston
motor, Not a pro, just a tinkerer...Try some checks. Did you take the lifters out and look? Lobe lift is the difference between a mike meas on the "base circle" and the lift . Compare the cams for wear and check the lift spec. My Intek had ground down its ex valve so that there was only 1/8 " lift and it still ran. (That cylinder finally went away). Stuck valves seem a bit of a mystery. Plane guys and some tractor guys see carbon (coke) buid-up as the culprit. This often happens on a very hot engine being shut down without reaching a reasonable temp. But in those cases bent pushrods are seen , or bent push rods drop out. I do not rebuild ac engines, but .003 guide oil clearance seems excessive. This may allow "cocking" of the stem in guide. You have not mentioned a guide seal. As you know these are used to control oil into the combustion chamber. I am surprised my Intake has a seal on the (? I think) ex valve as this is where the heat is generated. So with a seal the Briggs guys don't seem to want .003" oil film. I would carefully check all valve gear for cracks and wear and replace the springs. Hope some of this blather can help solve the problem or motivate the great forum knowers to respond, BTW removing and reinstalling valve guides did not work for me and BS does not sell guides (for my Intek , anyway), only assembled heads. My guess is that these engines fail mostly from valve mechanism problems if they are not fried from lack of oil/overwork. (As in using a 3 bagger on a hill with damp grass in 85F weather).:laughing:
I wouldn't think .003 is excessive at all. But I am thinking a car engine and don't know what the Briggs engine calls for. I would say go to the service manual and see what it dose call for because I was just guessing on that number. Oil dose take up space and you do need this space to lubricate the valve stems and without proper lube they will stick when they get hot.
#6
R
Rivets
R
Rivets
I don't feel that .003 is too great a clearance, but I would like to kno how you got that. You should have measured the valve stem with a mic at multiple places in the travel area. There should be no more than .001 difference in any of the measurements. You the measure the valve guide at the top, center and bottom with a small hole guage and mic. Again you should have no more than .001 difference between any measurements. The difference between the valve stem measurement and the valve guide measurement is your clearance.
Second, you never said what was the cause of the valve sticking in the first place and what corrective action you took. If the valve was bent or the guide tapered, you are spending a lot of time and effort for nothing.
Second, you never said what was the cause of the valve sticking in the first place and what corrective action you took. If the valve was bent or the guide tapered, you are spending a lot of time and effort for nothing.
#7
reynoldston
To be true full I am thinking back when I was working on truck engines about 25 years ago. They had replaceable valve guides and when you replaced one it had to be reamed. Its all part of a valve job on larger engines. Its just something I never got into on mower engines seeing I have never seen a replaceable valve guide in a small engine. Now I am not saying there isn't such a thing? If the valve guide is bad it is either new head or block time. Maybe oversize valve stems?? I think you have a very good point about the bent valve. I have never measured the valve stem clearance when I do a valve job on a small engine other then just by feel. I will assure you that .001 isn't something you will feel by hand.
reynoldston
I don't feel that .003 is too great a clearance, but I would like to kno how you got that. You should have measured the valve stem with a mic at multiple places in the travel area. There should be no more than .001 difference in any of the measurements. You the measure the valve guide at the top, center and bottom with a small hole guage and mic. Again you should have no more than .001 difference between any measurements. The difference between the valve stem measurement and the valve guide measurement is your clearance.
Second, you never said what was the cause of the valve sticking in the first place and what corrective action you took. If the valve was bent or the guide tapered, you are spending a lot of time and effort for nothing.
To be true full I am thinking back when I was working on truck engines about 25 years ago. They had replaceable valve guides and when you replaced one it had to be reamed. Its all part of a valve job on larger engines. Its just something I never got into on mower engines seeing I have never seen a replaceable valve guide in a small engine. Now I am not saying there isn't such a thing? If the valve guide is bad it is either new head or block time. Maybe oversize valve stems?? I think you have a very good point about the bent valve. I have never measured the valve stem clearance when I do a valve job on a small engine other then just by feel. I will assure you that .001 isn't something you will feel by hand.
#8
R
Rivets
R
Rivets
Briggs does have replacement valve guides. They are not that hard to replace if you have the correct tools. It used to be a common job to do so, but the labor costs today (about $50) lead most people to just decide not to go that route. We've gotten to be a throw away society wnen it comes to doing repairs on small engines. I used to do 25 rebuilds a year, but have only done 3 this year if my memory is still working. Reynoldston, you are correct, they must be reamed to size once they are installed, and most of the time I would install a new valve.
#9
M
motoman
M
motoman
There used to be a rocking check on stem to guide for some car engines. Raise valve off seat so much and then take side to side dial reading, but I guess that is something that would have to be worked out with geometry if not given by the mfgr. It was once fashionable to knurl valve guides to reduce the ID , then ream. The lands created by the knurling also held oil. I could not find any replacement guides for the Intek anywhere, including looking at motorcycle sites, only fully assembled heads. I suppose a lathe mod would work. Still believe Briggs knows (on Intek anyway) that guide problems mean softened head alloy so replace.
#10
reynoldston
reynoldston
knurl valve guides to reduce the ID
Now that you said something about it I remember that also. Its been a few years back for me and my memory isn't as good anymore. I still got the tools to grind valves but don't remember the last time I used them. On the small engines I just clean them up with grinding compound any more, I think they make valves and seats of better material now then in the older days. I don't care what is said older isn't better newer is.
Now that you said something about it I remember that also. Its been a few years back for me and my memory isn't as good anymore. I still got the tools to grind valves but don't remember the last time I used them. On the small engines I just clean them up with grinding compound any more, I think they make valves and seats of better material now then in the older days. I don't care what is said older isn't better newer is.
#11
motormonkey
Rivet, you are right.... I didn't say the cause of the valve sticking did i?
I know this much.. the issue is in the head... the valve wasn't bent, and the tappets aren't bent either... the cam.. showed some wear... I will try to get a few pictures tomorrow of the pieces... I am going to tear it down again....
I DID clean it up thoroughly(Head and piston head/block also the cylinder wall is spotless.)... sanding the valve stems lightly and lubing them before putting them back in.. after that, they moved beautifully in the valve guide.
This is a unique situation as I am currently traveling in a third world country... and I cannot get replacement parts here can't order them in either... international shipment costs like $100 bucks just to get a letter.
I was lucky to find a business that custom makes gaskets so I took the old headgasket and they made me a new one.
Update on the problem: I unstuck the valve via the valve spring access door and got the mower to run horribly for 30 seconds...
then to restart it I had to continue pulling the rope to kind of Help it stay running.. (it was running very slowly, obviously slow enough for me to pull the recoil along with it every 3 seconds to keep it running)
I guess it is also possible I got the valve tappets reversed... though that wouldn't explain the valve sticking in the head.. the only thing I can think of is the head is warped... and something happens with the expansion of the metal(perhaps exaggerating the warp in the valve guide when it heats up...?
this is frustrating trying to get it diagnosed correctly.. again, i'll try to take some pictures perhaps tomorrow maybe that will lead to some insight.
thanks everyone for your replies in the discussion.
motormonkey
I don't feel that .003 is too great a clearance, but I would like to kno how you got that. You should have measured the valve stem with a mic at multiple places in the travel area. There should be no more than .001 difference in any of the measurements. You the measure the valve guide at the top, center and bottom with a small hole guage and mic. Again you should have no more than .001 difference between any measurements. The difference between the valve stem measurement and the valve guide measurement is your clearance.
Second, you never said what was the cause of the valve sticking in the first place and what corrective action you took. If the valve was bent or the guide tapered, you are spending a lot of time and effort for nothing.
Rivet, you are right.... I didn't say the cause of the valve sticking did i?
I know this much.. the issue is in the head... the valve wasn't bent, and the tappets aren't bent either... the cam.. showed some wear... I will try to get a few pictures tomorrow of the pieces... I am going to tear it down again....
I DID clean it up thoroughly(Head and piston head/block also the cylinder wall is spotless.)... sanding the valve stems lightly and lubing them before putting them back in.. after that, they moved beautifully in the valve guide.
This is a unique situation as I am currently traveling in a third world country... and I cannot get replacement parts here can't order them in either... international shipment costs like $100 bucks just to get a letter.
I was lucky to find a business that custom makes gaskets so I took the old headgasket and they made me a new one.
Update on the problem: I unstuck the valve via the valve spring access door and got the mower to run horribly for 30 seconds...
then to restart it I had to continue pulling the rope to kind of Help it stay running.. (it was running very slowly, obviously slow enough for me to pull the recoil along with it every 3 seconds to keep it running)
I guess it is also possible I got the valve tappets reversed... though that wouldn't explain the valve sticking in the head.. the only thing I can think of is the head is warped... and something happens with the expansion of the metal(perhaps exaggerating the warp in the valve guide when it heats up...?
this is frustrating trying to get it diagnosed correctly.. again, i'll try to take some pictures perhaps tomorrow maybe that will lead to some insight.
thanks everyone for your replies in the discussion.
#12
reynoldston
reynoldston
I all my years of doing this work I never seen a valve stick unless there was a reason for it. rust? Broken valve spring? valve guide got hit some how? If the valve stem or valve guide aren't damage and you do have some stem clearance its something I sure don't understand. You said you are using homemade gaskets, maybe the gasket is too thin and the valve is hitting? A valve in a valve guide is a very simple mechanical thing. I am sure someone here has your answer.
#13
motormonkey
reynoldston,
I should have clarified... the gasket I had fabricated was done by a professional gasket maker.. they used the same material as the stock gaskets. that metal material in the middle with the gasket material surrounding it. same mic thickness.
I will try to get a video of the head while turning the flywheel.
motormonkey
I all my years of doing this work I never seen a valve stick unless there was a reason for it. rust? Broken valve spring? valve guide got hit some how? If the valve stem or valve guide aren't damage and you do have some stem clearance its something I sure don't understand. You said you are using homemade gaskets, maybe the gasket is too thin and the valve is hitting? A valve in a valve guide is a very simple mechanical thing. I am sure someone here has your answer.
reynoldston,
I should have clarified... the gasket I had fabricated was done by a professional gasket maker.. they used the same material as the stock gaskets. that metal material in the middle with the gasket material surrounding it. same mic thickness.
I will try to get a video of the head while turning the flywheel.
#14
M
motoman
M
motoman
Motor, Reread your original description...When the Intek cam was replaced I had to press off the drive gear from the cam. I don't remember exactly, but it must have been keyed. Could your cam have somehow sheared the cam drive gear key. So depending on heat the gear is spun outside the cam , making an index sound. Then when heat/cold allows the cam operates the valves, but out of time??:confused2:
#15
motormonkey
motoman,
That is a VERY interesting question.....
I will check that I have to tear it back down today...
Here is the video of manual rotation of the flywheel with the head off... i know this doesn't do a lot for us except we can see the timing etc.
motormonkey
Motor, Reread your original description...When the Intek cam was replaced I had to press off the drive gear from the cam. I don't remember exactly, but it must have been keyed. Could your cam have somehow sheared the cam drive gear key. So depending on heat the gear is spun outside the cam , making an index sound. Then when heat/cold allows the cam operates the valves, but out of time??:confused2:
motoman,
That is a VERY interesting question.....
I will check that I have to tear it back down today...
Here is the video of manual rotation of the flywheel with the head off... i know this doesn't do a lot for us except we can see the timing etc.
#16
H
hsherm
H
hsherm
After reading and re-reading your post, it sounds like the valves are not getting enough oil on them, thereby causing them to heat up and expand just enough to stick. Something you may want to check.
Just an observation is all.
Just an observation is all.
#17
motormonkey
motormonkey
Well hsherm,
UPDATE: I worked the valve over with WD-40 and it doesn't stick any more...
I wish I would have gotten a video of how it started up, because I can't find anything on youtube or the web in general that acts like it nor info on other similar cases.
but.. when I try to start the mower, it half-way starts up... I don't know how to describe it... basically.. I can pull the starter rope and it fires and runs for 1 second VERY slowly, (the Speed of the pull is the only way I know to describe it) then it dies.. I can almost keep it running if I keep pulling on the rope in time with the mower... it's going that slow.. and I dont get a LOT of resistence..
SO.. I am thinking my head-gasket is bad. I don't have any other conclusion if I had a compression gauge I would know but I don't right now.
I'm having a head gasket made for it and will be picking it up monday. (it's hand-made by an Artisan since there are none available and it costs $100+ in shipping to get one in where I am at right now)
UPDATE: I worked the valve over with WD-40 and it doesn't stick any more...
I wish I would have gotten a video of how it started up, because I can't find anything on youtube or the web in general that acts like it nor info on other similar cases.
but.. when I try to start the mower, it half-way starts up... I don't know how to describe it... basically.. I can pull the starter rope and it fires and runs for 1 second VERY slowly, (the Speed of the pull is the only way I know to describe it) then it dies.. I can almost keep it running if I keep pulling on the rope in time with the mower... it's going that slow.. and I dont get a LOT of resistence..
SO.. I am thinking my head-gasket is bad. I don't have any other conclusion if I had a compression gauge I would know but I don't right now.
I'm having a head gasket made for it and will be picking it up monday. (it's hand-made by an Artisan since there are none available and it costs $100+ in shipping to get one in where I am at right now)
After reading and re-reading your post, it sounds like the valves are not getting enough oil on them, thereby causing them to heat up and expand just enough to stick. Something you may want to check.
Just an observation is all.
#18
H
hsherm
H
hsherm
Thanks for sharing the video! I just watched it a few times (actually, quite a few times), and noticed a couple of things. The timing seems to be off by one "notch". (degree?) For example, the exhaust valve starts to open just before the piston reaches Bottom Dead Center (B.D.C), allowing for air and oil to be drawn into the combustion chamber. (The chamber acts as a vacuum at this point due to the combustion.) This then throws off the intake valve by the same amount; thereby lessening the amount of fuel that can be drawn in. I also noticed a slight amount of oil in the piston cylinder. This could be caused by bad rings, but it's more than likely caused by the "vacuum" effect drawing in air and oil through the exhaust port due to the exhaust valve opening before B.D.C.
It's been awhile since I've actually worked on small engines (mainly due to health reasons), so I'm making these observations from memory.
I hope this helps.
It's been awhile since I've actually worked on small engines (mainly due to health reasons), so I'm making these observations from memory.
I hope this helps.
#19
motormonkey
motormonkey
hsherm,
I am going to take another video of the timing for you while I have the head off.. I did get my head gasket back today though.
I think I am going to have to tear it down and re-time it because it seems way farther off than before.. and I might have to put a different cam in it (I think I have one from an identical spare parts mower.) though it did seem like it would have ran great if it weren't from low compression. I'll try to make a video and post it for you to see what you think.
Hey don't worry about making the observations from memory, I appreciate any ideas/help I receive.
Best Regards.
I am going to take another video of the timing for you while I have the head off.. I did get my head gasket back today though.
I think I am going to have to tear it down and re-time it because it seems way farther off than before.. and I might have to put a different cam in it (I think I have one from an identical spare parts mower.) though it did seem like it would have ran great if it weren't from low compression. I'll try to make a video and post it for you to see what you think.
Hey don't worry about making the observations from memory, I appreciate any ideas/help I receive.
Best Regards.
Thanks for sharing the video! I just watched it a few times (actually, quite a few times), and noticed a couple of things. The timing seems to be off by one "notch". (degree?) For example, the exhaust valve starts to open just before the piston reaches Bottom Dead Center (B.D.C), allowing for air and oil to be drawn into the combustion chamber. (The chamber acts as a vacuum at this point due to the combustion.) This then throws off the intake valve by the same amount; thereby lessening the amount of fuel that can be drawn in. I also noticed a slight amount of oil in the piston cylinder. This could be caused by bad rings, but it's more than likely caused by the "vacuum" effect drawing in air and oil through the exhaust port due to the exhaust valve opening before B.D.C.
It's been awhile since I've actually worked on small engines (mainly due to health reasons), so I'm making these observations from memory.
I hope this helps.
#20
P
Polaraco
I was going to say that. Thanks
When you put the valve back in the head, did slide up and down OK
Did you put some oil on the valve stem when you put it back in?
Poor mans valve grinding compound. Sand and grease. If it's an over head valve, you can use a electric drill. There's a 62 Chrysler 413 running around for 10 years now with that done to the heads.
P
Polaraco
knurl valve guides to reduce the ID
Now that you said something about it I remember that also. Its been a few years back for me and my memory isn't as good anymore. I still got the tools to grind valves but don't remember the last time I used them. On the small engines I just clean them up with grinding compound any more, I think they make valves and seats of better material now then in the older days. I don't care what is said older isn't better newer is.
I was going to say that. Thanks
When you put the valve back in the head, did slide up and down OK
Did you put some oil on the valve stem when you put it back in?
Poor mans valve grinding compound. Sand and grease. If it's an over head valve, you can use a electric drill. There's a 62 Chrysler 413 running around for 10 years now with that done to the heads.
#21
motormonkey
motormonkey
Polaraco,
I made sure the valve guides were extremely clean, then I oiled the valve stem put it back in and they moved like new.
the valves currently are functioning when I move the flywheel.
thanks for the tip on sand / grease.
I made sure the valve guides were extremely clean, then I oiled the valve stem put it back in and they moved like new.
the valves currently are functioning when I move the flywheel.
thanks for the tip on sand / grease.
I was going to say that. Thanks
When you put the valve back in the head, did slide up and down OK
Did you put some oil on the valve stem when you put it back in?
Poor mans valve grinding compound. Sand and grease. If it's an over head valve, you can use a electric drill. There's a 62 Chrysler 413 running around for 10 years now with that done to the heads.
#22
motormonkey
motormonkey
hsherm,
Here is the new video for opinions on timing before anything else!
Thanks!
Here is the new video for opinions on timing before anything else!
Thanks!
Thanks for sharing the video! I just watched it a few times (actually, quite a few times), and noticed a couple of things. The timing seems to be off by one "notch". (degree?) For example, the exhaust valve starts to open just before the piston reaches Bottom Dead Center (B.D.C), allowing for air and oil to be drawn into the combustion chamber. (The chamber acts as a vacuum at this point due to the combustion.) This then throws off the intake valve by the same amount; thereby lessening the amount of fuel that can be drawn in. I also noticed a slight amount of oil in the piston cylinder. This could be caused by bad rings, but it's more than likely caused by the "vacuum" effect drawing in air and oil through the exhaust port due to the exhaust valve opening before B.D.C.
It's been awhile since I've actually worked on small engines (mainly due to health reasons), so I'm making these observations from memory.
I hope this helps.
#23
P
Polaraco
P
Polaraco
I'm not is the position to watch the video right now, but something came to me earlier today.
Maybe the valve spring is weak. Or as said, you're not getting lubrication into the stem. Maybe the guide is worn so that the valve jams. (Key word there is Maybe) Does the valve have slop in the guide?
In big motors, a bad guide can cause a misfire. The valve will be sluggish and a small amount the vacuum is lost, drawing less fuel/air. Sort of like that. But that's a multi cylinder engine. I would imagine the principle is the same.
If it's not getting oil into the spring chamber, maybe the oil slinger is broken in the crankcase. (Do they still use those things?)
Don't mind me, I'm in the guessing mode with out it in my hands.
Maybe the valve spring is weak. Or as said, you're not getting lubrication into the stem. Maybe the guide is worn so that the valve jams. (Key word there is Maybe) Does the valve have slop in the guide?
In big motors, a bad guide can cause a misfire. The valve will be sluggish and a small amount the vacuum is lost, drawing less fuel/air. Sort of like that. But that's a multi cylinder engine. I would imagine the principle is the same.
If it's not getting oil into the spring chamber, maybe the oil slinger is broken in the crankcase. (Do they still use those things?)
Don't mind me, I'm in the guessing mode with out it in my hands.
#24
motormonkey
motormonkey
Polaraco,
Process of elimination is a good thing so no worries.
Yes they still use oil slingers, in this case instead of it being on the end of the piston cap it's a gear mechanism that rides on the camshaft gear.
yes it's getting oil. I think the whole problem boiled down to the mower having set for a long time and getting shellac from the old gas (ethanol perhaps) and sticking the valve.
The problem I was having was that I could pull start it but it ran so slow, that I could actually speed it up with the pull rope if I pulled in time with it every 1 - 2 seconds. which tells me it's not getting the compression to get up to speed I think.
I have a new head gasket for it, but I am debating tearing it down to verify the timing again before I put the new head gasket on because user: hsherm made the comment that my timing might possibly be off by 1 tooth (the matching up of the dots on the cam and the crank.)
I know I don't need to take the head off to be able to tear it down to the crank, but if I need/want to take the valves out again and i've already put the head gasket on I don't want to risk ruining it because I had to get it hand made.
Cheers and as always, I always thank everyone for their input!
Process of elimination is a good thing so no worries.
Yes they still use oil slingers, in this case instead of it being on the end of the piston cap it's a gear mechanism that rides on the camshaft gear.
yes it's getting oil. I think the whole problem boiled down to the mower having set for a long time and getting shellac from the old gas (ethanol perhaps) and sticking the valve.
The problem I was having was that I could pull start it but it ran so slow, that I could actually speed it up with the pull rope if I pulled in time with it every 1 - 2 seconds. which tells me it's not getting the compression to get up to speed I think.
I have a new head gasket for it, but I am debating tearing it down to verify the timing again before I put the new head gasket on because user: hsherm made the comment that my timing might possibly be off by 1 tooth (the matching up of the dots on the cam and the crank.)
I know I don't need to take the head off to be able to tear it down to the crank, but if I need/want to take the valves out again and i've already put the head gasket on I don't want to risk ruining it because I had to get it hand made.
Cheers and as always, I always thank everyone for their input!
I'm not is the position to watch the video right now, but something came to me earlier today.
Maybe the valve spring is weak. Or as said, you're not getting lubrication into the stem. Maybe the guide is worn so that the valve jams. (Key word there is Maybe) Does the valve have slop in the guide?
In big motors, a bad guide can cause a misfire. The valve will be sluggish and a small amount the vacuum is lost, drawing less fuel/air. Sort of like that. But that's a multi cylinder engine. I would imagine the principle is the same.
If it's not getting oil into the spring chamber, maybe the oil slinger is broken in the crankcase. (Do they still use those things?)
Don't mind me, I'm in the guessing mode with out it in my hands.
#25
motormonkey
motormonkey
motoman,
You hit the head on the nail, I was re-checking everything and this appeared....
Though this cam is not keyed like the intek cam it is pressed on... so when the valve stuck causing the engine to "knock" when pulling recoil was like putting the cam shaft in between 2 pairs of pliers.
the camshaft is one set of pliers.. and the stuck valve another... not allowing the cam to lift the lifter when needed it had no where to go but to break free when trying to go over the cam lifter.
You hit the head on the nail, I was re-checking everything and this appeared....
Though this cam is not keyed like the intek cam it is pressed on... so when the valve stuck causing the engine to "knock" when pulling recoil was like putting the cam shaft in between 2 pairs of pliers.
the camshaft is one set of pliers.. and the stuck valve another... not allowing the cam to lift the lifter when needed it had no where to go but to break free when trying to go over the cam lifter.
Motor, Reread your original description...When the Intek cam was replaced I had to press off the drive gear from the cam. I don't remember exactly, but it must have been keyed. Could your cam have somehow sheared the cam drive gear key. So depending on heat the gear is spun outside the cam , making an index sound. Then when heat/cold allows the cam operates the valves, but out of time??:confused2: