Brockport Bill 1,862 #1 Posted December 18, 2021 my manual for my 312-8 from 1989 for a Kohler M12 engine ( spec 471527 ) does not provide what the comprehension range or minimal pressure should be? Can someone tell me the desired range for generally healthy operating engine, as well as the minimum desired? Also - how about for the Kohler M10 ? thanks Share this post Link to post Share on other sites
RED-Z06 2,527 #2 Posted December 18, 2021 (edited) 26 minutes ago, Brockport Bill said: my manual for my 312-8 from 1989 for a Kohler M12 engine ( spec 471527 ) does not provide what the comprehension range or minimal pressure should be? Can someone tell me the desired range for generally healthy operating engine, as well as the minimum desired? Also - how about for the Kohler M10 ? thanks Most manufacturers dont provide a compression range because many factors can affect the test, speed, temp, valve lash, testing hose length, schrader or no Schrader in the test hose...you can easily test a healthy engine and show "low" if the engine is cranking slow, or the throttle is shut, cylinder dry, valve lash tight but in spec. These engines all had an internal compression release..so they will test low regardless In general if you roll the engine over by hand backwards and it bounces off the compression, that's good enough to run. Otherwise a leak down test is needed to show top end health. Edited December 18, 2021 by RED-Z06 5 Share this post Link to post Share on other sites
Maxwell-8 4,367 #3 Posted December 18, 2021 They have compressions decomps., only a leakdown test will give you a correct result 2 Share this post Link to post Share on other sites
953 nut 58,945 #4 Posted December 18, 2021 Your Kohler engine is equipped with a feature known as ACR (automatic compression release) which allows the exhaust valve to open slightly just prior to TDC (top Dead Center) on the compression stroke. This makes the engine much easier to start but it makes it imposable to do an accurate compression test. A leak-down test is the best way to evaluate the condition of your engine. the thread below tells you how it is done. 2 Share this post Link to post Share on other sites
Brockport Bill 1,862 #5 Posted December 18, 2021 7 hours ago, 953 nut said: Your Kohler engine is equipped with a feature known as ACR (automatic compression release) which allows the exhaust valve to open slightly just prior to TDC (top Dead Center) on the compression stroke. This makes the engine much easier to start but it makes it imposable to do an accurate compression test. A leak-down test is the best way to evaluate the condition of your engine. the thread below tells you how it is done. yikes..... that is an awesome thread - thanks - sorta wish i learned all this stuff decades ago - one of my gear head grandsons knows much of this stuff and when i ask him something he responds as if i should know the answer - - why? Because Grampys always have the answers to all the other toipcs we discuss ..hahahhahha 1 Share this post Link to post Share on other sites
