Ok I just installed a new motor (My old one blew up piston skirt shattered) I installed everything correctlt..I think! I got it running tonight with no issues it started right up with no issues. I let it idle for about 5 minutes just to let it heat up check fluids etc. I shut it off a few times and it started back up with no issues. So im standing there and all of a sudden it goes wide open so I shut the key off....it still ran, turned of the on\off switch...still wide open running!!!! So i figure let me yank the plug wire...I did and made sure there was no arc and it was far away to not spark.....still wide open running!!!!! so in a last effort I unscrewed the top of the carb that houses the throtle assy and ripped it out and it finally shut off......WHAT THE $%$%$#% happened!!! has anyone ever heard of this ??? there are no kinks in the wires the throttle works fine as far as the cables go but im afraid to try and start it again without someone giving me asvice on this or if they ever heard of this! HELP!!! Ive been working on this thing for over 2 mos!! I just want to get it running correctly!
Dave

 

can you say F#@k. how in the heck was it still running without any spark to the plug. I have never heard of this before. I was thinking about rebuilding mine because I don't want the skirt busting on mine and have to replace the entire bottom and top end. sorry not to be any help but good luck.

 

it was probably still running because of the compression, that is pretty weird tho.

 

a lean condition will rev up a motor

 

if it is a two stroke it will happen if it gets to hot. I worked at a yamaha dealer and had it happen to me on an RD 350, same as banshee but air cooled motor. Any way it happened while I was riding it, alk about scary, this is called instintaniuos combustion. When the chamber reaches a high heat range it will run with no spark at all. You can pull the plug wires, kill the ignition and it won't do crap. If I were you I would check your cooloing suystems, fans coolent etc. Once it is all cooled down you should be able to start it and let it run for a couple seconds before it does it agin, just don't let it run at wot for long.

 

There is a couple thing that might do that. One is that there is a piece of something on the head or was in that got hot enough to keep ignition going like some cars do called run on. Is this a 400 or the 500 motor? Im guessing withe the skirt shattering it was the 400 I had the same thing happen to mine. Did you get all the pieces of the skirt out? To break in a 2 stroke motor leaving it just ideal is not the rightway. You need to ride it an just not run it wide open try to run it a diff speeds up an down for a about 5 pass about 50yards each then run it like normal this is how I was told to do break in from HPD. Did you add extra oil to the gas to run it rich with oil for the break in too.

 

ok people thank you for the help first off!! I fixed it. I doublecheked the coolant and bled it and decided to not use the oil injection and just mix the gas 32.1. Fired it up and let er run for a while and it seemed to be fine. Took it for a little ride down the road and its fine. So it turns out it was the heat issue or not getting any oil so all is well!!

 

Make sure to check for leaks in the intake. The fuel charge left in the motor can mix with air and auto ignite. As long as it can still get fuel and air it will stay running. If it's a small leak you can flood it with the choke to shut it down. I've heard of it happening when some one cracked their case. Be prepared to throw it in nuetral and shut of the fuel if this happens again.

 

This is what happens when you have no oil in the mix.I blew the motor(piston and rings)in my old '85 Tecate 3 wheeler when the f-ing thing dieseled its way to oblivion.Pulled the fuel hose to shut it off.Good luck man.

 

The right way to keep this from happening is don't let it. That's one of the reasons you aren't supposed to run the motor without a belt on it. High rpm's with no load ususlly gets the ball in motion, choking the carb is generally the way to cure it. Put your hand right over the end if you can. The fuel coming in actually cools down the combustion chamber, gets it out of diesel mode. Don't know how oil would have anything to do with it?