20 HP Kawasaki Runs Rough When Warmed Up

[tbengal]

This is the FD620D, liquid cool used in a 2086 Cub Cadet Super Garden Tractor. Recently, it will run rough only after I am done with 1 hour of mowing. It appears as soon as I turn the PTO off, as I am preparing to park the lawnmower back into the barn. It starts right up when cold, but when the rough running appears, there is some black smoke puffs at the exhaust, but not when mowing (no signs of roughness). This last time it occurred, I had the lawnmower turned off for about 10 minutes, installed a spark checker on both plugs, turned the lawnmower on, and the roughness was mostly gone, spark was good on both plugs.

Engine history: Built around 1995, 550 hours, electric solenoid on carb was replaced 3 years ago, plastic cam was replaced 1 year ago along with both sparkplug coils, ground wires were all replaced 1 year ago.

Is there something getting really hot that is causing this problem?

 

[jharvey]

Tim
Have you checked the air filter? Mine gets wet inside the air cleaner assy due to crankcase vapors routed in there to be burned. This causes the paper element to plug. I change the foam pre- cleaner frequently and the paper filter at least twice a season now. When hot it starts hard and puts out some black smoke showing it's got a really rich mixture. Clean filters make mine better. On a good note -1362 hours and still doesn't need oil added between changes. JH

 

[edale]

Black or dark smoke usually means it's burning rich. Why it's burning rich could be a bunch of things. here are a few guesses.

Under load (with pto on) the engine is spitting fuel into the filter area soaking the filter. but is running so hard it can use the extra fuel. when the pto is shut off the extra fuel (plus the fact that the filter isn't pass enough air) it burns rich. Check you exhaust valve clearance.

Maybe the float valve in the carb is sticking. and staying in the wide open position after hard use. Open the float bowl and clean the valve and seat. Replace both if they seem sticky. Check for fuel in the flat too.

My last guess is the engine might be overheating a bit. An over heating engine under heavy use can sometimes run rich without blowing smoke. clean the engine and radiator of dust dirt and grass clippings. is there a cooling fan? check the blades.

good luck

-everettdale

 

[tbengal]

I see someone else is also experiencing a wet air filter. Mine always has a coating of oil in it, but I never have to add any!

Yes, there is a cooling fan. I will look to see if it is moving when the engine is running. I usually clean out the metal screen in front of the radiator, and there is coolant in the overflow tank.

I plan on adjusting the valves first, then maybe tear into the carb. I just discovered that Kawasaki does not make a carb rebuild kit, according to the local JD dealer. A person has to order the items separately and have it cost more! The float needle can be replaced separately, but the seat is part of the float body, so the body has to be replaced if a new seat is required!

 

[tbengal]

Here is the latest. I have done nothing to the engine except the following. I just remembered that about a month before my problem started, I had filled the gas tank up too much. About a day or two later I had gas seeping out of the cap onto the floor (sun shining onto tank). When I first seen this, I took a paper towel and wiped off the top of the dirty/gassy cap. I made a point of blowing into the air bleed hole just 7 days ago. I have since mowed twice and the tractor is running smooth when going back into the barn. Do you think this is a solution?