Rapid acceleration and kill switch doesn't work?

[Mitch_McComb]

This is a strange problem, but it's happened a couple times now.
After riding half to full throttle and comming to a coast, the quad will wind out like I've got the throttle pinned. Tonight I'm going to lube my throttle cable, check the carb slide, etc... but the kicker is, when it's doing this.. I can't turn it off with the kill switch. I have to dump a gear and let it stall. I can then kick it back to running and idle is correct and the kill switch works.

I thought the kill switch stops the spark plug from sparking? Is it possible that being pinned full throttle can somehow keep a spark?

I've got a 86 motor with 86 wiring (Stock kill switch assembly)

Any ideas?

Thanks!

Oh yea, anybody know a good cheap place to get a-arm bushings and shock bushings?

[wilkin250r]

It's called a runaway condition, or lean runaway.

Your engine develops a hot spot. It gets so hot that it will ignite fuel on it's own, at that point the spark doesn't matter. It feeds on itself, as the engine revs more, it creates more heat, which ignites fuel better, which causes the engine to rev more.

It's not running off the spark anymore, so pulling the kill switch doesn't do any good. There are a few different ways to kill the engine, but stalling it is the best. The other option would be to choke off the air, or let it run out of fuel. Stalling is obviously the easy choice.

Now, you should be looking at why this is happening.

You could be running a little lean.

You could have some sort of carbon deposit or something in your engine that is creating the hot spot.

You could have the wrong heat-range plug, and need to switch to a colder plug.

[250r4life]

hmm... man, i had kind of the same thing happen about 5 years ago on my banshee... i was sitting racing the hill (at the dunes) several times, and then i came back to my group and as i rolled to where i was gunna be stopped, i popped it into neutral and sat there for about 3 seconds, and all of the sudden my bike just started racing like i had it pinned... well it kind of freaked me out, so i hit the kill switch, nothing, turned the key off, nothing, then i reached down and pulled off both spark plug wires at the same time, and it stopped after that... maybe it was a coincidence that it stopped when i pulled the wires, i dont know??? but it freaked me out and ive always wondered what the heck had happened. i'm still unsure though. that was my 1st trip out on that bike, and i had it for another year after that. i rode the piss out of it- probably an avg of 2-3 times a week, several more dune trips, and i never changed the jetting or anything and never had another problem with the bike. it was a great bike... so, any ideas wilkin? thats always boggled my mind...

[beerock]

the spark plug becomes a glow plug like in diesels.

[wilkin250r]

Originally posted by 250r4life
so, any ideas wilkin? thats always boggled my mind...

I have no idea. Pulling the spark plug wires shouldn't have any effect, just like the kill switch.

[E-ATV-Racing]

It sound like the bike was running out of gas or the the float sticks closed and the bowl is empty. When it is nearly empty it will become very lean and rev very high. It will stop once all the fuel is gone. This could explain why it stopped when you pulled the plugs, just good timing.

[robyone]

richards bushings are reasonably priced, mine held up good too.