What is wrong with my 92 KX250?

[kxrider92]

My 92 kx250 is having some issues that have me confused. When i start it it will idle fine for a second then it runs wide open and i dont even have to touch the throttle it has never had this problem before.anyone know what the deal is?When i ride it sometimes it will open up into the band for just a second then it falls on its face.

[Hillclimb#42]

Right at start-up, with choke on, it starts bang, bang, bang, waaaaaaaaaaaaah, then idles back down to bang bang bang, or fouls the plug? Then with a new plug runs fine?

If so, my 250 was like that for awhile. When I first bought it, I thought it was just a trait of the bike, but was cured with a float adjustment. I'm sure thats not the only possible cause and it may be a coincidence that it fixed it. Like if it was debris, that was also taken care of while i was in there setting the floats. Something in the pilot jet is also a good place to look, or in the floats or holding up the gas flow, or possible air leak from a seal, gasket or carb clamp.
Check floats, the tab that pushes the pin down in, is tweekable.

[kxrider92]

I adjusted the float it idles fine now but when i crack on the throttle it just starts to come into the band then it just goes waaahwaahwaaah like its on a rev limiter

[Hillclimb#42]

Sounds like an air leak, like base gasket or head gasket, or your slide is hanging up for some reason. Sometimes the cable housing can hang up on the top of carb, or at throttle housing, sometimes the brass fitting on top of carb is broke, sometimes there's just no slack in the cable, or even a worn slide will hang. To check for slide problem, you have to remove again, look into carb and make sure the slide closes all the way. Whacks closed when you release the throttle. Also crap in the slow jet will lean it out. I always blow through them onto white paper to see if something comes out. Air leaks around gaskets usually appear wet or oily at the problem spot. This is a bad problem that will melt your rings. Investigate closely and fix before starting again.