Stumbling Kohler

[ghost1]

Just replaced head on CV20 for a neighbor as intake valve seat had collapsed. Engine runs fine until pto is engaged then seems to act like it's running rich. He had replaced carb thinking that was the original issue with engine. I have checked adjustment with governor and went through carb. It acts like it needs a high speed carb adjustment, however, there is none to adjust. Any ideas?

 

[Lawnranger]

A rich stumble can many times behave the same as a lean stumble.

You mentioned that it "seems to act like its running rich" but what have you done to actually confirm that it is running rich?

 

[ghost1]

Not sure how to test, other than checking plugs

 

[bertsmobile1]

There is a wonderful tool called a colortune.
They come from Gunsons in the UK do not know if they have a USA agent.
Should be a part of every amateur mechanics tool box.
I use mine ( got 4 ) almost daily and they have quite literally saved me thousands over the 40 years since I started using one.
Gunson | G4074 | Colortune Single Plug Kit

Other than that you can slip a piece of white card behind the exhaust and check for black smoke but you might need to stand on your head to do it.

A shorting out clutch will put a try high load on the engine so momentarily the engine will run way too slow so run rich.

There is a damping spring on the governor arm to throttle rod and while it principle job is to smooth out throttle changes, if not fitted or stretched too far it can allow too great a throttle opening , again causing a momentary richness.

 

[mechanic mark]

http://www.kohlerengines.com/onlinecatalog/pdf/24_690_07_EN.pdf

 

[ghost1]

Pulled plugs and both appear to be burning clean (no soot). Engine sound like it is on the verge of running smooth, but just wont build up the rpm's to do so. Almost sounds like a miss or possible valve issue. Have also ran with and without an air filter and changed to fuel filter.

 

[Lawnranger]

Pulled plugs and both appear to be burning clean (no soot). Engine sound like it is on the verge of running smooth, but just wont build up the rpm's to do so. Almost sounds like a miss or possible valve issue. Have also ran with and without an air filter and changed to fuel filter.

Thank you for the rest of the story, or at least part of it. Now, is there anything else you have done or checked or tested or verified or anything else you can tell us so we don't send you down the wrong path?

Whenever an engine shows up at my shop that has the symptom(s) yours has I check for manifold vacuum leaks by spraying carburetor cleaner around all the intake manifold connections while the engine is running and listen for a change in RPM. Next, I test the coils with an adjustable spark checker. I use this one because you can run the engine safely under load (blades engaged) with it installed: Amazon.com : Oppama PET-4000 Adjustable Gap Inline Spark Tester Echo 99051130023 : Patio, Lawn & Garden Yes, it's pricey but if you are going to do this kind of work you will have to spend some money on test tools or you can just start changing parts until you replace the bad part but as we all know the latter is the more expensive way to go.

Of course there is more to it but the above is where I start and once you verify the above then you can go on to other tests and as you probably figured out there will be more test tools involved.

Let us know your test results.

 

[ghost1]

First let me say that I am by no means a professional mechanic. A neighbor with a Dixie Chopper Kohler CV20 was mowing and engine quit running. He assumed it was the carburetor and purchased a new one but still wouldn't start. When it got to me, checked for compression and found one cylinder was reading zero. Pulled head to find that intake valve had been dislodged and setting at an angle not allowing valve to close. Replaced head and when engine would not fire, found fuel tanks to have water in them from mower being stored outside with a broken fuel cap. Drained tanks and engine started and ran fine. After about a month, got a call to say mower again had quit and wouldn't fire. Pulled plug from replaced head and found electrode to be smashed. Again pulled head and something made from metal (never found), had gotten into head and caused extensive pock marks to head, valves, bent both pushrods, and smashed top of piston to where it locked rings. Replaced piston, push rods, and took head to local machine shop and after inspection, it was determined that even with marks, head and valves were ok to use. Compression on repaired cylinder is 120 and other cylinder is 140. That pretty much takes us to today. Mower will start and run fine. When PTO is engaged, it acts like it has a miss and won't quite build the rpm's to smooth out.

 

[ajwgator]

Not sure on a CV20 but I have a CV22 on a Woods M2250 (actually made by Gravely for Woods) and the engine started acting as you have described. It had about 900 hours on it at the time and tried the carb cleaning which didn't make any difference. After a doing more research I found that the carb has a vacuum actuated accelerator pump in it. I took the carb back off and sure enough the diaphragm was deteriorated and letting fuel get into the vacuum side. This part is not included in the carb kit so has to be purchased separately. The damn thing is was close to $80... for just a gasket and diaphragm! Anyway, once I got that in and all back on the engine it ran like a striped ape again.... smooth as silk.

Maybe worth looking into on the CV20.... Hope you find the solution.

 

[ghost1]

Thanks for info about carb. It does have a new carb on it that's just over month old. Will tear it down and see if anything may be clogging a jet. Just ran it around the yard a few times and it is almost acting like only running on one cylinder, however, both plugs are getting spark.