Good range would be 90 to 100psi
Most of these small air cooled engines don't have a lot of compression but off course it does need some. During my time in repairing these all i would do would be to remove the flywheel screen and one plug at a time. Using a piece of stiff plastic or a hammer handle give the flywheel a very hard flip in the opposite direction to it's original travel, if it brings up and bounces back in the proper direction it would normally turn then the compression should be sufficient. Then repeat this procedure again by re installing the spark plug and remove the other one. You can check each cylinder one at a time with this procedure. Normally i don't think the manufacturers give the specs for the compression ratios in psi.
SOURCE: Kohler Command 12.5 OHV engine on John Deere STX
Have you tried pouring a little fuel into the plug hole and try for start? If it runs for a short time, you have fuel delivery problems. Check the fuel filter for plugging. Look under the carburetor bowl for a small solenoid that commonly sticks in one position. I'm not aware of an automatic compression release on these engines. As this is a 4-stroke engine, it's possible that one of the valve clearances has closed up during use. Check this with the piston at top-dead-center on the compression stroke. Hope some of this helps!
SOURCE: when does 25 command kohler fire on magnet
It fires when the left edge of the magnet is precisely aligned with the left edge of the left leg of each coil. (When viewed from the flywheel and looking straight on at the coils.)
Hope this helps,
Dolf-
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SOURCE: 15 HP OHV Kohler engine with no compression
Have you checked for a bad head gasket?
Check the intake valve springs or the intake valve shafts to be sure they aren't stuck open. Another cause could be excessive carbon build up on the intake valve causing them to not seal.
If you've gone this far, you could try a compression leak down test. If you still have the push rods out, you can use or get an adapter that will allow you to pressurize the cylinder(s) with air by removing the spark plug. Apply 70-80 psi air directly to the cylinder (the cylinder may go to BDC (bottom dead center) but if you don't have any push rods, the valves can't open.
Listen carefully - if you hear air leaking out of the carb, it's a bad intake valve. If you hear air from the exhaust, it's an exhaust valve. If you hear air from the crankcase breather, it's piston rings.
SOURCE: We are replacing head gaskets
first torque to 16ft/lbs in a x patt. then 30ft/lbs in a x patt. for head the intake gaskets connecting to the head should be 12 to 17
SOURCE: how much compression should a kohler 25 hp engine
hi there
there are no published compression limits for kohler
the prefered method is to have the cylinders leak tested , because of the decompressor action built in while trying to compression test
but off the top of my head most machines would run best with a minimum of 100 psi or better
given that these have a compression ratio of 9:1
you could work it out
9:1 X 14.7 PSI ( 1 amtmosphere ) @ sea level = 131.00 psi
compression ratio = swept cylinder volume + clearance volume (@ tdc) divided by clearance volume
here is web site for obtaing service manual
http://www.kohlerplus.com/main_frame.asp
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select command pro twin -ch/cv 17-26
go to service manuals , select sm 24-690-07 file is 8.82 Mb and double click it and save a copy to your hard drive
cheers hope it helps
pauly46
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