Alright so the other day I was riding in the snow we had. Finished riding and put the quad away and I shut the fuel off but let the motor keep running so there wasn't a lot of fuel sitting in the carb. Pulled the choke out to half so it wouldn't run lean and let it run. After about 30 seconds the rpm started to climb. Then I decided enough fuel has been burnt and to shut off the quad but when I shut the kill switch to off the rpms shot up and it sounded like the throttle was wide open. Kill switch was off and I thought quick enough to use my gloves in my hand to cover the exhaust and essentially plug up the motor to kill it. Took a few seconds to think to myself "wtf was that about?" So I Kicked it back on and toggled the kill switch off and it shut off just fine. Any ideas that could have caused this? I didn't turn the handlebars or pull the throttle cable i just switched the KS To off and the motor just revved up.
Runaway motor
- Thread starter JohnnyBertone
- Start date
you're gonna fry the top end if you keep doing that "no fuel sitting in the carb" run it till it leans out trick.
less/no fuel to a running engine = very lean = boom !
absolutely no need to drain the carb bowl, unless it's going to sit for months, and thats what the bowl drain screw is for.
less/no fuel to a running engine = very lean = boom !
absolutely no need to drain the carb bowl, unless it's going to sit for months, and thats what the bowl drain screw is for.
Turning the kill switch off just stops the spark. In a crazy lean condition (like you running the carb empty) might have made it so that the build up of compression was so high it ignited the little fuel that was in it without a spark. High compression + very lean mixture = high temp spike (possibly high enough to ignite with no spark)
Like Awk said, don't run it dry like that. Its bad for the motor and there is a simple way to drain the carb without running it dry.
Like Awk said, don't run it dry like that. Its bad for the motor and there is a simple way to drain the carb without running it dry.
Sounds like .. Pre ignition due to high heat igniting the fuel with out any need of spark. High heat like this is typically caused by lean conditions
alright so now i know to not let it run the carb out a little lol i figured it was just running off compression and high heat but i wasn't sure
Compression doesn't change. With leaning out, chamber and plug temperatures go up and the plug glows white hot like a glowplug in an RC engine, pre-igniting the mixture. It is often called dieseling.
Steve
Steve
