I have an Emark Z turn mower with a 26 hp Kohler engine. It appears to only have compression on one cylinder. You can see the piston making strokes and has no noises like thrown rod. Both cylinders have fire. While running I can disconnect the plug wire on the good side and mower dies. Disconnect the plug wire on the other side and there is no change in the engine. Any ideas?

Are you making the assumption of no compressin based on the diagnostics stated here "While running I can disconnect the plug wire on the good side and mower dies". This could be a sign of a bad ignition coil. Check for spark by removing coil wire (spark plug lead) put a new spark plug in it and ground the plug to the engine, crank and look for spark. If you do NOT have compression on that cylinder and the piston is moving, pull the valve cover on that side and look for a valve that is not closing. They can gum up and stay in the open position. When that happens it can also cause the rocker to loose its connection to the push rod because all clearance and tension was lost. You will need to readjust valve clearance.

Regards,
Don

Have you tried it? I had another customer with the same problem and am curious.
Regards,
Don

I did swap sides with the ignition coils and changed plugs. That did not change anything. So I guess due to process of elimination it is probably the valves. I haven't been able to work on the mower for a while. When I am able to get back on the machine I will keep you informed of the results.

Do A Compression Test On The Cylinders.

Just an update on the Kohler. I replaced the bent exhaust push rod. Still no compression. Then I removed the #1 head and found the exhaust valve seat was out of it's position and caught under the exhaust valve which hit on the piston. In so doing it damaged the top of the piston. Short blocks are I've found are $800. Ouch!! At least I know now what the problem was.

That really sucks!! Go Kohler.

Don

I have had the same problem here and found it wash the push rod. It was bent from over reving the motor so I was told. I pulled the ohv cover and you could clearly see the problem ordered the part from a kohler dealer not to exspensive
Took care of the problem