Seeking to Better Understand ACR on Kohler CV20S

saktate

LawnSite Member
Location
New Orleans
I don’t have a problem with my Kohler CV20S engine. I just want to better understand why a compression test will be inaccurate because of the automotive compression release valve mechanism. Does the ACR cause the compression test numbers to be lower on both cylinders, one cylinder, which cylinder? I’m ready to be schooled. Thank you.
 
OP
saktate

saktate

LawnSite Member
Location
New Orleans
Yes sir, I saw a couple videos that demonstrate the ACR in action and it appears that only one exhaust valve is involved, but I couldn’t determine which cylinder was effected from looking at the cam.
 

JoeRagMan

LawnSite Senior Member
Location
Near TMI
I would think it effects both cylinders on the exhaust valve. That’s why a “leak down “ test is recommended. Bring one cylinder 1/4 turn past TDC and perform the test. Do one cylinder and then reposition the other cylinder the same way to test the other cylinder. YouTube is your friend.
 

JagT20N

Inactive
Location
will county Il
if its a hsp model its both , some do not have acr at all ( the one out of a 90's sears tractor I have doesn't have it ) unless its really bad with rings , most acrs will keep you in the 90-100 psi range ( which is within Oem spec , below 90 find the fault ) both cylinders are ussually with in 10% of each other , a leak down tester is the best way to go as it also can point to a valve that has a carbon build up / sticking and causing a leak ( which will cause a burned valve eventually ) or is burn't as you will hear the air leak in the muffler or carb . you can buy the tester cheap online thru jegs or summit racing .
 
OP
saktate

saktate

LawnSite Member
Location
New Orleans
if its a hsp model its both , some do not have acr at all ( the one out of a 90's sears tractor I have doesn't have it ) unless its really bad with rings , most acrs will keep you in the 90-100 psi range ( which is within Oem spec , below 90 find the fault ) both cylinders are ussually with in 10% of each other , a leak down tester is the best way to go as it also can point to a valve that has a carbon build up / sticking and causing a leak ( which will cause a burned valve eventually ) or is burn't as you will hear the air leak in the muffler or carb . you can buy the tester cheap online thru jegs or summit racing .
I have much to learn. Appreciate the info!
 

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