Kart engine running with plug cap off!

[Blue_SV650S]

Now correct me if I am wrong, but when you take the spark plug cap off, an engine should stop pretty quickly right?!!? ... not keep revving higher!!!

I started my DD kart engine with an 'off board' electric starter (its for my mates 'clutched' one) - it seemed to start up and run OK, then revved up by itself (throttle was NOT jammed open).

Sh1111tttttt ... I need to stop this I thought ... so quickly took took the plug cap off to kill the engine (take away the spark) it kept going - flat out!!! ... what now?!?!? .... I therefore ran to the other side and 'choked' the airbox (put my hand over the inlet) to smother then engine and stop it!!

https://www.youtube.com/watch?v=ZfeGMkubktA&fmt=18
____________________
The purpose of life is to fight maturity.

[Dr. DaveJPS]

is it potentially running like a diesel?
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"intelligent inattention is preferable to unintelligent tinkering"
www.davejps.com

[binge]

My old scooter used to do this. It turned out to be running so bloody hot that the plug would be glowing. And even when I killed it at the keys, It would keep running until it had cooled down to a low enough temperature for the plug to stop glowing red hot, And the engine to stall.



Could be way off, But just a suggestion.





Ben

[chillpill]

lol has got me stumped , binge is probly on the right lines if the engine was warm when it did it

[Blue_SV650S]

[chillpill]

dodgy low octane fuel maybe ?

[G]

Gav (Hex) had it happen on his minitmoto; with an auto-clutch it was a bit of a problem to stop. Airbox was hidden away and exhaust was pretty hot. Ended up having to take the sparkplug out... while trying to work out whether it was best to try and slow it down or just rev as highly as it wanted.

Had it happen on my KTM 350 a couple of times (with kill switch on), but that was a case of rear brake fully on, then slowly release clutch to slow engine down a bit, before dumping clutch to stall.

[Blue_SV650S]

[SoND]

I've shocked the fuck out of myself when pulling the plug lead off my scooter when it was running one time. Should this have happened?
____________________
Go back to bed - You have no rights - "Streetfighters ~ Mainstream motorcycling's crackwhore sister."

[Blue_SV650S]

[chillpill]

[chillpill]

lol tell us , i cant be arsed to wait for keith to come along to figure out exactly what happend in a matter of nano seconds lol

[chillpill]

plug red hot and crank case seals gone sucking in air and gearbox oil ?

[finpos]

Engine is dieseling - remarkably easy to do on most carbed engines, just hold the throttle right open as you switch off the ignition, a lot of the time it will keep on going, although if it is at full revs it would seem to indicate the throttle is open (i.e. it's not being throttled!)

Possibly throttle is being held partially open by the choke?

See: Anti-dieseling solenoid.

f.

[Pete.]

[Blue_SV650S]

The throttle was not opened or faulty ....

Well my postmortem revealed a shiny ring round the crown of the piston (i.e. no carbon deposits) and a matching shiny spot on the head. The ring was jammed in the piston, so there had been contact and it had slightly squashed the top of the piston.

The main bearings had a bit of play and I think this coupled with a very tight 'squish' meant one thing hit the other!

I'm fairly sure that one of the main seals popped out slightly (letting air in) which caused the revving - I only noticed that when I replaced the bearings (and put the new seals in - they sat back further than the ones I took out) ... so it was actually a combination of the two that killed the engine!
____________________
The purpose of life is to fight maturity.

[chillpill]

im sticking with my last answer , even if it was letting in more air it wouldn't be revving high like that unless there was extra fuel to burn with it (gearbox oil)

[Blue_SV650S]

[SoND]

[chillpill]

crap , wenever someone mentions kart engine i just think rotax