After help here with a head gasket diagnosis, I replace the gasket and adjusted the valves, but compression is so high. The engine will barely turn over unless I cover the intake. Pulled the crank case cover, and the camshaft and compression release is intact. I figured I made a mistake adjusting the valves, so after reassembly adjusted them again and compression is still far too high. I’m stumped. Any advice.? Thanks in advance.
Compression release and valves are correct, but compression too high?
- Thread starter Mattdad1
- Start date
There are 2 TDC strokes in a 4 stroke engine. Which one did you use?
Sounds like the ACR is not working. Temp gap the valves to 0.002" and see if the ACR works again.
Did you hand rotate the engine while checking the valves verifying your gap was proper?
Decarbonize the cylinder. It's in yours and every other small engine manual known to man.
Sounds like the ACR is not working. Temp gap the valves to 0.002" and see if the ACR works again.
Did you hand rotate the engine while checking the valves verifying your gap was proper?
Decarbonize the cylinder. It's in yours and every other small engine manual known to man.
I don't see any ID numbers posted for the engine.
If it's a single cylinder Briggs Intek the valves are not adjusted at TDC per the manual specifications, go 1/4 inch down ATDC and set the intake valve at a snug .002 or even .0015 (as slomo says) and turn the engine over by hand few times CW with the spark plug out and monitor the INTAKE valve lash. (I've seen it go wider sometimes right after adjustments is why I say rotate the engine and re-check.
Next. You have to go slow and keep a good eye open for this. (this will let you SEE if the intake valve compression release is trying to dump/release any compression after you have set the INTAKE valve lash to a snug .0015-.002. Back the engine up backwards from TDC on compression stroke (CCW of the flywheel if looking down on a vertical shaft engine flywheel) to where the piston is going down by about 1/2 way (couple inches down) in the cylinder then slowly come up CW on the compression stroke and carefully watch the INTAKE valve's rocker arm for a slight dip in the rocker arm (it should dip down little bit then back up just before TDC) at about 1/4 to 1/2 inch before the piston reaches TDC. This dip in the rocker arm is the compression release momentarily slightly opening and dumping some of the compression by cracking open the intake valve just Before Top Dead Center (BTDC). You can monitor the position of the piston by using a long slim screwdriver into the spark plug hole. Just be sure you do not electrically crank the engine when the screwdriver is inserted.
Have you actually checked the compression? If not give us a compression reading from a gauge. (sometimes a weak electrical crank system will appear to be compression issues)Using another battery and good jumper cables will give you a hint about such. (also a weak starter can cause such) Placing the hand over the carb intake and getting a crank over is starving the engine of air so as to reduce the compression somewhat. This is what the ACR is suppose to do by slightly opening the intake valve and dumping some compression just before the piston reaches TDC.
You might also try cranking the engine over electrically with the spark plug wire off and the spark plug installed. If it cranks over with fire to the plug the timing is slightly too fast due to partly sheared flywheel key.
Also be sure the engine is not flooding and hydrolocking. Gas being spit out the spark plug hole is an indicator of such.
If it's a single cylinder Briggs Intek the valves are not adjusted at TDC per the manual specifications, go 1/4 inch down ATDC and set the intake valve at a snug .002 or even .0015 (as slomo says) and turn the engine over by hand few times CW with the spark plug out and monitor the INTAKE valve lash. (I've seen it go wider sometimes right after adjustments is why I say rotate the engine and re-check.
Next. You have to go slow and keep a good eye open for this. (this will let you SEE if the intake valve compression release is trying to dump/release any compression after you have set the INTAKE valve lash to a snug .0015-.002. Back the engine up backwards from TDC on compression stroke (CCW of the flywheel if looking down on a vertical shaft engine flywheel) to where the piston is going down by about 1/2 way (couple inches down) in the cylinder then slowly come up CW on the compression stroke and carefully watch the INTAKE valve's rocker arm for a slight dip in the rocker arm (it should dip down little bit then back up just before TDC) at about 1/4 to 1/2 inch before the piston reaches TDC. This dip in the rocker arm is the compression release momentarily slightly opening and dumping some of the compression by cracking open the intake valve just Before Top Dead Center (BTDC). You can monitor the position of the piston by using a long slim screwdriver into the spark plug hole. Just be sure you do not electrically crank the engine when the screwdriver is inserted.
Have you actually checked the compression? If not give us a compression reading from a gauge. (sometimes a weak electrical crank system will appear to be compression issues)Using another battery and good jumper cables will give you a hint about such. (also a weak starter can cause such) Placing the hand over the carb intake and getting a crank over is starving the engine of air so as to reduce the compression somewhat. This is what the ACR is suppose to do by slightly opening the intake valve and dumping some compression just before the piston reaches TDC.
You might also try cranking the engine over electrically with the spark plug wire off and the spark plug installed. If it cranks over with fire to the plug the timing is slightly too fast due to partly sheared flywheel key.
Also be sure the engine is not flooding and hydrolocking. Gas being spit out the spark plug hole is an indicator of such.
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On what stroke?
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It just easier to adjust the rocker when the opposite rocker is fully the valve. Also the intake valve is the one closest to the oil pan.
bertsmobile1
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What Slomo is trying to say is are you sure you set the valve lash on the compression stroke rather than the exhaust stroke
The "tests" is to check the valve lash at TDC twice
So set the lash, rotate the engine 1 revolution and check the lash
If it is bigger on the second check then you set the lash on the exhaust stroke not the compression stroke which is quite a common mistake when you use the TDC method , particularly when the cam is getting a bit old so the inlet opens a touch later & the exhaust closes a touch sooner .
Why do you think that the compression is too high ?
The "tests" is to check the valve lash at TDC twice
So set the lash, rotate the engine 1 revolution and check the lash
If it is bigger on the second check then you set the lash on the exhaust stroke not the compression stroke which is quite a common mistake when you use the TDC method , particularly when the cam is getting a bit old so the inlet opens a touch later & the exhaust closes a touch sooner .
Why do you think that the compression is too high ?
Thanks all. Feeling stupid. Used the wrong valve clearance engine is running fine. Now just waiting for the ACR for the head gasket to fail again. What a crap design.. Thanks for the help!
Good to hear you got it going.
Read post #6 and get familiar with that procedure so as the next time you have to adjust the lash, just rotate the engine so as a valve's rocker arm is fully DOWN and then adjust the opposite rocker.
It's a no brainer and but we usually do not mention this procedure at first to a newbie because it is not ever mentioned in the Briggs engine SERVICE MANUALS.
You do not have to fool around trying to figure out if the piston and valves are on the TDC compression stroke.
On your model of engine after you adjust the lash turn the engine over 2-3 times without starting the engine and re-check the lash again BEFORE calling it good and installing the valve cover for a crank/run test because sometimes the valve lash will increase and just .002-.003 increase can result in compression lock again.
Read post #6 and get familiar with that procedure so as the next time you have to adjust the lash, just rotate the engine so as a valve's rocker arm is fully DOWN and then adjust the opposite rocker.
It's a no brainer and but we usually do not mention this procedure at first to a newbie because it is not ever mentioned in the Briggs engine SERVICE MANUALS.
You do not have to fool around trying to figure out if the piston and valves are on the TDC compression stroke.
On your model of engine after you adjust the lash turn the engine over 2-3 times without starting the engine and re-check the lash again BEFORE calling it good and installing the valve cover for a crank/run test because sometimes the valve lash will increase and just .002-.003 increase can result in compression lock again.
bertsmobile1
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You are not alone most of us have done it at some time
Now go mow
Now go mow