84 atc250r need help

[tyman2395]

Hey guys I'm new to the forums and 3-wheelers, I got a 84 250r yesterday, The wiring is kinda messed up so I spliced 2 wires together and it got spark. Also i have my ktm525xc coil on it, So anyways I started it up and it was idling kinda high so I put the choke off and then like 5 seconds later it is revving wide open ( i mean WIDE open) So I ripped the wires off and still running and took the spark plug cap off (which should of killed the motor) and it was still running wide open, We had to turn the gas off and let it run out before it turned off. Anyone know what could have caused that? thanks.

[dcreel]

Maybe a short, I don't know if using the wrong coil would do that. The carb might be varnished open. A long time ago some friends and I were messing around with an old 2 stroke dirtbike that had been sitting outside for years. We got spark and started kicking it to see what would happen. It fired up revving to the moon with the clutch stuck on engage. This thing took my friends brother for an 8 second ride that rivaled that of a bull ride bouncing off of walls, cars, and anything else in his back yard until somebody jerked all of the electronics out from under the tank in a handful. I don't know how high it was revving but it seemed to be a lot higher than it should have.

[tyman2395]

The carb is all cleaned, The guy mixed the fuel 40:1 but isn't it supposed to be 20:1 ? would that cause it?

[big danno]

Nope 40 to 1 wont make it do that but a crank seal will if it gets ripped or the slide is in backwards or the thottle cable is sticking.As for running after you pulled the plug wire off,it was only running on pre ignition.
When I get a new project that maybe has not run for a while or I dont know the last time it ran I always leave the carb to air box boot off so that I can put my hand over the carb to choke it off so it does not over rev like that and cause more problems.Only when I am sure the engine will not take off and rev will I put the boot back on.
Do you still have spark? I ask this because you mave have killed the cdi box when you pulled the plug wire off to try to get it to shut off.If you do still have spark then pull the fly wheel off and replace the crank seal on that side and also check the level of oil in the gear box to make sure it is full because if that side seal is pooched then at least it wont suck air but it will suck fluid which will cause it to smoke like crazy but not rev out of control or burn a piston.
Ideally on any old or even not so old two stroke machine (sled trike or what ever) you should replace the crank seals because they get old and get brittle or shrink.Many peaple do not realize how important these seals are to a two stroke engine and thnk that the seals never need to get changed and all of a sudden you have a burnt piston or something even worse and a large repair bill to make it rite.At that point it seems real cheap to have had the seals replaced but of course it is too late at that point.
Good luck with your trike as they are aolt of fun when the do run properly