HELP! Kohler command 20 problem!

[Westbrooklawn]

As I previously posted, I am having trouble with my Kohler command 20 on a Walker with 48" GHS. It is running rough, missing, and slight consistent backfire while running.

I have drained and cleaned gas tank, lines, and carb. Installed new gas filter, air filter and plugs. Still running rough, and seems to be overheating very quickly, even after only a couple of minutes of running at idle. The high heat seems to be coming from only the front cylinder, to the point it heats the muffler to cherry red where that cylinder exhausts into the muffler....and only after a couple of minutes of running. Could this be a stuck or burnt valve? How can I test for that? I can borrow a compression guage, but not sure how to run the test properly. I know there are some great mechanics on this site......any suggestions??? Thanks!!

[barnard]

definately sounds like aburned valve . Or else atight one. Disconnect the spark plug wires. set throttle in wde open position and crank it over a couple of seconds. (after removing the plug and while holding the compression tester in the spark hole-very firmly) . the compression should be 100-120 range.

[Ryan Lightning]

Just incase you didnt know, Kohler has a 2 year warranty. Im guessing yours is older though?

[Westbrooklawn]

Yep....5 years old....out of luck!!!

[Westbrooklawn]

Finally got around to checking the compression......both cylinders are right at 170. I guess this means it's not a burnt valve? I am thinking now that it might be the coils.....but not sure how I can test them. Any suggestions would be appreciated.

[captdevo]

compression looks good.

stuck valve is possible, or weak/broken valve spring. squirt a little marvel mystery oil in the cylinders and start it, or squirt some in the carb throat as it's running..(do this outside, it's gonna smoke)

does it run rough as soon as you start it, or does it happen after it heats up?

does it start easily cold/hot?

cooling fins clean?

pull valve cover and inspect.

maybe blown head gasket.

could have dirty carb., causing it to run lean.

flywheel key sheared enough to offset timing and cause misfire.

[Westbrooklawn]

Captdevo -

Thanks for the reply. To answer your questions, it starts easily both cold and hot, runs rough from the start but gets worse as it warms up, cooling fins are clean now but were not when this problem started, I've pulled both valve covers and valves seem to be operating properly while running, have cleaned carb out, and hadn't hit anything that would have sheared flywheel key. Also if head gasket was blown wouldn't compression have leaked down after I stopped cranking and let it sit? Any further suggesions would be greatly appreciated!!

[captdevo]

the fins were clogged.

you probably have a blown head gasket, i've seen the compression tests show good and still have a blown head gasket, even a scored cylinder for that matter.

i've seen them blown through into an oil port.

when you removed the valve cover, was there severe dark discoloration around either valve?

you don't necessarily have to hit anything for a key to shear, they can shear on a compression stroke or when an engine is shut down and reverses rotation.

i would bet $$ you have a blown head gasket though, especially if the fins were clogged enough to overheat the engine

[Westbrooklawn]

Hmmmmm......... Thanks again for the reply...... I'm not a mechanic by any stretch of the imagination, but I have found I can fix about anything if I have the right instructions (either verbal or written manual). I guess I need to go ahead and pull the head. Hope it's as simple as a blown gasket! Any other helpful hints are always appreciated.

[John DiMartino]

When a Command blows a head gasket 99% of the time it blows it into the pushrod galley.I believe you have a blown intake gasket,This is just my educated guess.You do not have a blown head gasket if you have 170PSi on both cylinders,IMO.With it running spray some carb cleaner or starting fluid around the intake of the front cylinder,if it picks up ,and smooths out,youve found the problem. BTW with an intake gasket blown the front cyl will run really lean,and that will explain the red exhaust ,and high cyl temp,and lean missfiring/backfiring. John D

[captdevo]

Westbrooklawn,

What did you ever find wrong with your 20hp?


Dave

[Westbrooklawn]

Well Captdevo, both you and John were right. Just got it back from the shop yesterday and it had a leaking intake gasket and a blown head gasket both. Replaced both, and rebuilt carb, and it is running like new!

I gave up on it myself, and finally got it to Kohler mechanic in Hillsborough, NC. A 76 year old gentleman (Wade Griffin) that sells and services Grasshopper mowers only, but he will also work on Kohler engines regardless of what they are on. I was really impressed with his knowledge, honesty, and fair prices.

I consider him a real find as he works without any advertising.....for both mower sales and engine repair. Lucked up on him from a recommendation from Kohler.