run away 2 stroke

[ronnyg]

Well heres a interesting dilemma, just got my kxt 250 running, was sitting there idling when it revved right out by its self, to the point the kill switch wouldn't shut it off! Had to pull the pug lead....wow... what could cause this? Any idea's?

[tri again]

Hi and welcome.
Try the search key with the words
"death rev"

Apparently 2 strokes can run like that without spark
or kill switch doesn't kill it.
Most opt for stalling them in gear.
All I have 2 stroke is a chainsaw but there should be every answer to all your questions on here.

[emmie357]

Could be an air leak causing it to run lean.
May need to be leak tested.

[Tri z250]

Where in bc are you

[ronnyg]

Im in Christina lake

[danbur55]

my 93 Polaris trail boss 250 was doing that right after I rebuilt the motor one crank seal must have got damaged when I put it together changed both seals helped a bunch but then would take a long time to return to idle found trash in pilot jet now it runs great

[jeswinehart]

When 2 strokes start starving for fuel they rev wayyyy up. If it was "dieseling" from being hot (don't sound like yours was) pulling spark plug lead would have no affect. Had it happen on a Polaris scrambler at TrikeFest a few years back, had to shut fuel off and let run out of gas.
Or, air leak as suggested.

[emmie357]

When it happened to me it was a leaking crank seal.

[muthey]

it is definitely a lean condition somewhere, time to tear into your fuel delivery and all your seals to find the problems. I would do a leak down test on it as well.

[barnett468]

If you're not sure how to do a leak down test, check out the video below. It also shows cheap tools you can buy to do it with.
You obviously need to remove the flywheel and clutch cover to check the crank seals.

If you take the parts off, a shop might do it for around $60.00.

http://www.youtube.com/watch?v=zdq7NRcUIp8

[JasonB]

Clogged pilot jet can do that, open the throttle wfo or flip the choke up it will die right away. Clean that carb and go buy an inline fuel filter! I had my 500r do it at trikefest 2013 and once more at the badlands. Give it full throttle it will die.

[ronnyg]

Thanks for the info gonna leak test it on Monday!

[tri again]

When 2 strokes start starving for fuel they rev wayyyy up. If it was "dieseling" from being hot (don't sound like yours was) pulling spark plug lead would have no affect. Had it happen on a Polaris scrambler at TrikeFest a few years back, had to shut fuel off and let run out of gas.
Or, air leak as suggested.

Oh, you mean like the old gas powered airplanes?
.o49 little engines with a glow plug?
Battery to glow plug, get it started and it would run without glowplug and you knew when it was running out of gas because it would roughly double in rpm's for 10-20 seconds before it ran all the way out of fuel.
Might that be considered a 2 stroke diesel type of definition?

[tri again]

I wonder why I've never experienced this with any of my chainsaws.
and I've had saws in almost every state of condition and for decades.

...just trying to understand

[jeswinehart]

I wonder why I've never experienced this with any of my chainsaws.
and I've had saws in almost every state of condition and for decades.

...just trying to understand

If you get them hot enough,,,, just below the seizing temp,,, you will experience it.

[Atc70noob]

Are you running premium fuel? If you run regular fuel on the high compression two strokes they will diesel and cause dings on the inside of your head. I learned that the hard way.

[just ben]

If It was Idling fine (with the choke off) and suddenly started revving high,my best bet would be either the bowl was going dry or a partially clogged pilot jet. if it were a seal or any other air leak It would have revved high from the get go. If it happens again put it in gear and kill it with the rear brake.

[Ethan1]

I had a polaris scambler 90 do this the chain poped off and it reved right out i hit the choke and it died