Hi all, Last year I stripped the engine on my 05 rev3, and replaced the seals, all was running great for about 4/5 trials, then, midway through a trial the engine started to rev it's bits off! And I couldn't shut it off, in the end it seized up and I had to have a new piston and relined barrel. I have checked the carb and the slide is running smoothly and shutting off crisply, the cable is ok and moves freely, has anyone any idea what caused this as I'm about to start her up for the first time, and I don't want to blow the engine again.I also checked the reeds and they were ok. Thanks Tony.

I'm no expert and probably telling you things you allready know but, when I had this happen it was the throttle cable jammed holding the slide wide open, bloody scary!!

Only other thing that I know can be an air leak, could it be on the inlet stub between carb and engine?? Good luck with it and post up what the problem was when you find it.

Hi tone 27 if any bike starts revving out put your hand over the end of the exhaust. Saved me a couple of times. Good luck.

Pre ignition can cause a runaway as it does not require a spark to ignite the mix, may explain why the kill switch didn't work

Phone around and look for a shop who can pressure test your engine, eliminate air leak as a possibility

Thanks guys, 0007, what causes pre ignition?

Well, it's abnormal combustion, glowing carbon buildup, a burr on the head gasket etc

It takes a couple of things to start it and it isn't good for the motor, but again a leak test of your engine should be done to rule out crank seal, crankcase and intake leaks

It puts several psi air pressure in the engine and crankcase and you look for air leaks with soapy water at trans vent, intake manifold, base gasket etc

An air leak is essentially an extra air intake, it should never happen in a sealed engine

But I did have a high comp 2 stroke years ago that would runaway as the float bowl went low (running out of fuel), first place to look is fuel delivery problems

Did the bike have a heavy fall before it revved to death? I've fell off mine like this before and whilst on its side it also revved.

Hand over or gloved thumb in the exhaust will stop it though.

Mine was fine once upright again though. Have your thumb ready in case!

A recent fall to the right down a grassy bank caused the outer cable on my throttle to get pulled out of the rubber sealing boot on the Domino throttle assembly. When i restarted the bike it revved like mad, and only my memory of putting hand over the exhaust saved it.

I then checked the bike and restarted her without noticing the dispaced cable outer......and the same thing happened. It was only after a more thorough investigation i found the problem....

regards

Ian