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captsomer
04-19-2010, 11:46 AM
Hello All,

I have a Kohler that is giving me problems. Its a CH22 twin cylinder horizontal shaft engine mounted in a Cub Cadet tractor with about 500 hours on it. It starts fine. After a few minutes of running it gets real weak. Just turning on the belly mower or aggressively climbing a steep hill bogs it down bad and almost kills it.

I suspected that it was only running on one cylinder so I put it away in the garage to be looked at later. The next day I tested the spark at both cylinders. Tested fine. I checked compression and both cylinders also checked fine. Just for kicks, I checked the fuel supply. The hose coming out of the pump was running very strong. I gave the carb a quick cleaning and put it back on. I put it all back together and started to mow a little grass. It was running fine up until about ten minutes into it when it started to get weak again. I quick limped back to the garage and checked spark and compression. Both were fine.

This time, I removed all of the front engine shrouds and heat shields along with the entire exhaust system. I fired up the engine and it ran fine (loud but fine). I felt with my hand, that the exhaust from each cylinder was hitting very strong signifying that each was firing strong. I took of mowing grass with the loud engine. This time, about five minutes into it, it started running weak and I could feel / hear that the left side cylinder had stopped hitting. Once in a while it would hit a couple of times, but for the most part, it was freeloading and not running.

I removed the valve cover and pushed on the valves and they seemed ok.

I'm stumped. I think its either a valve that gets hung up once the engine warms up or a bad spark that gets lazy when it gets hot.

Does anyone have any experience like this? Which direction should I go? Advise?

laman
04-19-2010, 12:13 PM
Coil maybe acting up when hot...

GlynnC
04-19-2010, 12:34 PM
The engine shrouds are a critical part of cooling--forcing air around the cooling fins. Don't run long without the shroud--you'll have an overheated engine.

I'm guessing the coil might be heating up--that's a guess!

piston slapper
04-19-2010, 01:29 PM
Try pulling the choke a little to see if the cylinder comes back online , if it does, its a leaking intake gasket.

Ch22's may have smartspark ign system , If you coils have 2 small wires plugged into them, It is a SAM module system with HEI coils. you need an ohmeter to check these coils.To do a quick check, When the engine warms up and drops a cylinder, pull the sparkplug wire off to isolate the bad coil. If you replace the coil, make sure to set the airgap at .013, if you dont you will have misfiring issues.

captsomer
04-19-2010, 03:19 PM
Thanks for the input guys. I was kind of leaning toward the ignition problem myself. I wanted to see if anyone else had done battle with this problem before and what the results were. I'll order a coil pack and go from there.

captsomer
04-22-2010, 11:53 PM
I have to remove the entire engine from the tractor to swap the coil pack. This is going to take longer than I thought.

It was pretty dirty when I opened up the cowling. Lots of crud in the cooling fins. I pressure washed it clean while it was out. Could this have caused overheating / my problem?

piston slapper
04-23-2010, 11:58 AM
Good bet...When air cooled engines stop cooling, they stop being engines.

captsomer
04-23-2010, 06:21 PM
OK. I put on the new coil pack (left cylinder) cleaned the cooling fins and everything, new plugs, new fuel, new fuel filter, splashed a little carb cleaner in the tank just for kicks and I STILL HAVE THE PROBLEM!!! :hammerhead:

I checked spark in both cylinders, both good and strong.

While it was running poorly, I pulled the left plug wire. The RPM's dropped slightly and it got a tad bit rougher, maybe. Next, I pulled the right side plug wire. It started running like crap big time! It was back firing flames out the exhaust end everything. It scared the hell out of me. I thought I'd been shot!:laugh:

Guys, I'm running out of ideas. I'm thinking its a valve issue in the left cylinder, but the compression test still reads OK. Could it still be a valve issue? The carb is clean. Choking it doesn't affect the problem much, if at all. Neither does throttle. I really don't think its fuel related. The sparks are hot and there isn't much in the timing to adjust so I'm kind of ruling out ignition too.

I'm not afraid to pull the head and see, but I was just trying to wrap my brain around what this could be and hear from you guys first. I may have time for it this weekend.

Thanks

wcb607a
04-23-2010, 08:21 PM
check the value guides or the value guide seals. That will make the engine loose power.

GlynnC
04-23-2010, 11:50 PM
Don't know if this happens with mower engines--but my brother-in-law recently had a small utility tractor acting this same way--it had a cracked head. When the engine heated up, the crack expanded. His was easy to recognize the problem because cooling water ran into the motor oil. The cracked head did not show up in a compression check.

captsomer
04-24-2010, 12:56 AM
Don't know if this happens with mower engines--but my brother-in-law recently had a small utility tractor acting this same way--it had a cracked head. When the engine heated up, the crack expanded. His was easy to recognize the problem because cooling water ran into the motor oil. The cracked head did not show up in a compression check.

I'm starting to think like you. I have ruled out (I think) everything else except compression issues. Valves, cracks, seals, etc. I can't wait to find out what it is! This is bugging me.

I don't know if this means anything but when I first started it up after all of this work, it was running rough and was belching LOTS of white smoke out the exhaust. I fogged my entire yard! It did this for a good two minutes. I shut it down and fired it up later in the day and it was not smoking anymore. It was just running bad. At the time I figured it was just the carb burping itself into action or something. The engine stood upright the entire time so I don't think it was oil leaking into the cylinders. Water from the pressure washer cleaning maybe? I wouldn't think water would last that long though. Would stuck valves do this?

VegetiveSteam
04-26-2010, 12:08 PM
You say the compression is ok. Can you tell us what compression actually is? Thanks.

piston slapper
04-26-2010, 02:00 PM
Sounds like you went from bad to worse. make sure your coils are gapped at .013 (very important) and recheck all wiring connections , connectors need to fit snug. Your engine didnt like the bath you gave it.

Normal compression on command twins is 180 psi. 160 is ok , However there should not be more than 10 psi difference between the cylinders.

captsomer
05-20-2010, 10:06 AM
Hey Guys, I'm back. It took me a while to get back to this project but I got it taken care of now.

I pulled the head on the #2 cylinder (the intermittent one) and everything looked great. I put it back together.

Next, I pulled that Spark Advance module box that mounts on the side of the engine. It seems that that was the problem. I didn't think that it could only fail on one cylinder. Thats why I didn't look into it earlier.

Any way, I put everything back together and she is purring like a kitten again. All that trouble from a little black box.


I should have known...

Thanks for all of the input on this guys.