Some of you may have seen my JS550 thread over in the Kawasaki section. Basically I've been having trouble getting the ski to idle and it will randomly 'runaway' like a deisel. Killing the spark does nothing. The only way to stop it is to choke it out or prime it and flood it.
Hopefully this thread will help someone down the road and save a few engines. The first time it happened to me I was in a panic trying to stop the engine before it blew.
SO - I'd like to hear some of your thoughts/opinions on the subject.
Engine Runaway
Engine runaway is when the motor revs up freely on it's own. Preignition is taking place in which no spark is needed. A red spark plug or peice of glowing carbon preignites the fuel mixture and causes engine to continue picking up speed until failure.
Causes
In order for this to happen, there has to be a lean condition present. Any kind of air leak could potentially lead to destruction. Intake gaskets, carb gaskets and crank seals seem to be common culprits.
I'm guessing a pourly tuned carb could also be a problem? I'm starting to think my crank seals are fine but my high mixture screw is too lean. The ski has higher compression than stock but I think we adjusted the carb back to stock for a starting point.
How to stop it
I was absolutely shocked when my ski started to runaway. I immediately grabbed the spark wires and it continued to pick up speed. My second reaction was to put my hand over the intake but my flame arrester plate was still on, so I wasn't able to choke it out with my hand. Finally I grabbed my primer and pumped it a few times to flood it. Shew!
Hopefully this thread will help someone down the road and save a few engines. The first time it happened to me I was in a panic trying to stop the engine before it blew.
SO - I'd like to hear some of your thoughts/opinions on the subject.
Engine Runaway
Engine runaway is when the motor revs up freely on it's own. Preignition is taking place in which no spark is needed. A red spark plug or peice of glowing carbon preignites the fuel mixture and causes engine to continue picking up speed until failure.
Causes
In order for this to happen, there has to be a lean condition present. Any kind of air leak could potentially lead to destruction. Intake gaskets, carb gaskets and crank seals seem to be common culprits.
I'm guessing a pourly tuned carb could also be a problem? I'm starting to think my crank seals are fine but my high mixture screw is too lean. The ski has higher compression than stock but I think we adjusted the carb back to stock for a starting point.
How to stop it
I was absolutely shocked when my ski started to runaway. I immediately grabbed the spark wires and it continued to pick up speed. My second reaction was to put my hand over the intake but my flame arrester plate was still on, so I wasn't able to choke it out with my hand. Finally I grabbed my primer and pumped it a few times to flood it. Shew!