2084 cylinder cutting out?
 

2084, 20hp.kohler,1050 hrs.

After the tractor runs for a while it will bog down like a large chunk of dried grass dropped off the deck and into the blades, if you understand the sound. It seems like the governor kicks it back up right away but the engine kicks and knocks a few times, sometimes puffs out some black smoke, and if it happens long enough, which is usually 5-7 seconds, it smells like it is running rich.
After acting up a few seconds it continues to run perfect. Today during 2+ hrs. of cutting it probably did this about six times.

This has been happening for a while now. Within the last 50hrs. or so I had the heads off and de-carboned everything so I know that has nothing to do with it.

I was wondering if one of the ignition modules was cutting out every now and then and how could I check them.
When it happens under load with the blades spinning, it happens and goes away so quickly, there is no time to pull a spark plug wire to see if that cylinder stopped firing.
Any body ever experience the above?

Thanks, Ed.

You're probably on the right track with the coil(s) possibly going bad. with 1050 hrs and 20 years on them, it might be time. These are known to go bad on the Commands. You CAN replace them without pulling the motor, by disconnecting the firewall and moving it back enough to expose the flywheel cover/fan shroud, but if you have the time and wherewithal to pull the motor, it's worth it to give it a good cleaning and check for other potential issues that you may not see while it's bolted up to the tractor. The Command block is suprisingly light weight and you should be able to lift it out without too much strain. Otherwise, hook up an inline tester one side at a time with the side panels and hood removed, and try to look for missing spark when the stumble occurs - but it's going to be hard to see unless you're mowing in the dark! You could also get a pair of insulated pliers and pull a plug wire while it's running under load and see if it replicates the condition.

I'd come nearer to saying that you have a valve hanging up, or bad gas/water in fuel. Does it smoke black when it stumbles?

If it was a magneto, it wouldn't come right back.

When I cleaned the carbon off the pistons, heads,etc., I cleaned the valve stems too and they were not tight in the guides. This was done about 50hrs. ago.

Fuel is fresh at each cutting, at worst a week old.

Sometimes a puff of black smoke and the smell of running rich when it stumbles.
I wouldn't say a large cloud of black smoke.

Thanks, Ed.

They may not have been tight in the guides when it was cold. How about when it gets hot?? No way to tell if the clearance was correct unless you ran a gauge through it. How did you clean the valve stem and guide??

It may be electrical, but I really don't think so. Could be a problem with a safety switch, making it cut out. Really don't think it's a mag issue though. Take the hood off and run it. That way you can see what the governor is doing. Could also be a sticky float/seat causing the carb to occasionally over-fill and flood. I know, really not much help, but not really enough info to work with. :bigthink:

When my ignition module was going bad it would start and run on one cylinder for a few seconds and then the other cylinder would cut in and run as it should. I was able to pull the plug wire and that confirmed that the cylinder was not firing.

You can change the module without removing the engine but I found it much easier to unbolt the engine and slide it ahead a couple inches and then you can get both your hand and your head in.

Cleaned the valves up with a wire wheel,cleaned the valve guides with a brass brush and brake cleaner.
I was also thinking of a safety switch. I think I may by-pass them for the next cutting and see if that helps. When it did happen, I wiggled the key a bit but there was no difference so I think the ignition switch is good.

I've had the engine out a few times so that is no big deal if I need to do it again.

Thanks, Ed.

You should not clean the valve stem with a wire wheel on a grinder. Could possibly leave a perpendicular abrasion that will cause the valve to stick. Brass brush only, by hand on the stem.

Was it acting up before you pulled the heads? :bigthink:

Looking back at my record book it was 70hrs. since I cleaned the valves and carbon not 50hrs. as I said earlier. I think if there was an abrasion on the valve stem it would show up sooner rather than later.

It did not act up before pulling the heads and has run flawlessly for 70hrs. since before starting to act up.

Thanks, Ed.

Eslenk,

Does the engine sound like it's running differently (missing, spitting, sputtering, backfiring) when it does this or does it just sort of bog down like it's not getting the gas it needs while engine is still running smoothly.

You mentioned a puff of smoke. Are you sure it smells like gas or could it be oil that your smelling?

Remove your air filter, is there a puddle of oil inside the filter area by the carburetor opening and is the filter soaked with oil?

I do maintenance/repairs on my friends 2084, 20hp kohler magnum. I just had a situation where the Crankcase Breather gasket (RTV sealant) had failed and was allowing pressurized oil to fill the breather area then get sucked up into the air filter area and into the carb. If the engine was running at a constant speed eventually it would gather enough oil by the carb opening and suck some in. The engine would bog briefly, a puff of smoke and then run fine again until it rested the cycle. If you have an oil saturated filter and pure oil poured/sucked into the carb it might be enough to cause this issue. I replaced the Crankcase Breather gasket and my problem was solved.