QuestionQUESTION: I have a Kawasaki 20 hp air cooled motor that has been fouling the right plug while I'm mowing. I can pull the plug and clean it and in an hour it will foul.I've installed new plugs(NGK BPR4ES), fuel filter and air cleaner. The plug fouls with carbon which can easily be cleaned. I usually mow at about half travel speed capabilities. This last time I mowed at full travel speed and checked the plugs after mowing about 2 acres and the plugs were clean. After the mower sat for a day, I started it and it started rough a blew blue smoke like it was flooded. After it cleared it ran fine. Any ideas? Could it be a carb problem? Stuck choke maybe?
ANSWER: When you say you mow at 1/2 speed and the plug fowls and when ran at full speed it did not fowl is part of the issue. The engine is an air cooled engine and has to be operated at full speed all the time. It is like trolling with a large outboard engine. If it is not opened up and operated at full speed it will fowl the plugs and this is a water cooled engine. The engine requires cooling when operated. The pitch of the flywheel fins and the cooling fins on the cylinder and the recommended operating speed are all tied together to properly cool the engine. Not cooling the engine will cause the plug to fowl.
The other thing that can cause the plug to fowl is the coil. It could be giving you intermittent spark and the only way to fix it is replace the coil. It could also be valves not seating in the one cylinder. Maybe a head gasket, they would all have to be inspected.
As far as the blue smoke and the engine stalling it comes from burning foul. More than likely there is a small air leak in the crankcase at the oil fill tube or dipstick. You should check the oil to be sure there is no gasoline in it. You would notice the the oil level has risen. If it is the inlet needle in the carb is not seating. Clean and install a new needle and seat. I hope I have helped.
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QUESTION: When I say I mow at half speed I'm referring to the travel speed. The motor itself is always running wide open.That's what I find strange. Why would the plug foul if my travel speed changes from slow to fast. The motor itself is always running wide open,that never changes.
AnswerSorry, you are correct travel speed should have nothing to do with one spark plug fowling one thing can be the valves on the cylinder are not set properly. If the intake valve is staying open allowing too much fuel to get an the cylinder that could do it. excessive pressure in crankcase could also but I'm surprised it's only in one cylinder this would come from a leak in the crankcase. it could be at the crankcase gasket oil dipstick or oil filled to name some of the normal places.
You also said there was a cloud of blue smoke. Blue smoke is oil burning. The only way for it to get into the combustion chamber would be past the valves stems into the crankcase breather and then in through the carburetor because the breather hooks up to the back of the air filter assembly. If it was excessive enough once the breather fill oil could be pumped up past the valves seat and if a valve is not seating it would let oil pump into the cylinder.
The only other thing would be intermittent spark on one cylinder I would suspect the coil because it does not happen on both sides. Both plugs fouling would indicate an intermittent safety switch or intermittent ground. I hope some of this information helps.
