Too much compression. adjusted the valves and it got worse

2ball

Well-Known Member
Joined
Jul 29, 2020
Threads
24
Messages
128
  • / Too much compression. adjusted the valves and it got worse
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?
 
Last edited:

Bertrrr

Well-Known Member
Joined
Mar 11, 2021
Threads
5
Messages
406
  • / Too much compression. adjusted the valves and it got worse
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.
 

ILENGINE

Lawn Pro
Joined
May 6, 2010
Threads
39
Messages
9,940
  • / Too much compression. adjusted the valves and it got worse
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.
 

2ball

Well-Known Member
Joined
Jul 29, 2020
Threads
24
Messages
128
  • / Too much compression. adjusted the valves and it got worse
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.
 

2ball

Well-Known Member
Joined
Jul 29, 2020
Threads
24
Messages
128
  • / Too much compression. adjusted the valves and it got worse
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?
 
Last edited:

Rivets

Lawn Royalty
Joined
Mar 11, 2012
Threads
55
Messages
14,749
  • / Too much compression. adjusted the valves and it got worse
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.
 

2ball

Well-Known Member
Joined
Jul 29, 2020
Threads
24
Messages
128
  • / Too much compression. adjusted the valves and it got worse
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.
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!

Oh and Chickanic on Youtube says I may have a Camshaft issue!
 
Last edited:

sgkent

Lawn Addict
Joined
Sep 27, 2017
Threads
30
Messages
1,679
  • / Too much compression. adjusted the valves and it got worse
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).
 

2ball

Well-Known Member
Joined
Jul 29, 2020
Threads
24
Messages
128
  • / Too much compression. adjusted the valves and it got worse
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).
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.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,702
  • / Too much compression. adjusted the valves and it got worse
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 .
 
Last edited:
Top