runaway two stroke

[Kawasakinut]

i got a situation maybe yall can enlighten me on . okay stuation 1996 125
recently rebuilt and would not start. now this is a buddies bike and i was like well let me try and see what i can do to get it running or started. so i kick it a few times and nothing, so i take the plug out and there was spark, so i cross that off the list. now i didn't do a compression or leakdown but it seemed to have compression. so i'm fuel, electrical or mechanical so no noticable mechanical issues so i go to fuel. i take the carb off blow it out all passages working no noticable defects or broken parts. so i look in the manual and the air  screw was not set right it was all the way in  the spec was like out 2 turns so i make the adjustment recheck the diagram against the spec chart to make sure i am adjusting the right screw. so i put the carb back on and proceed to kick this bike over about the third kick it sputters. i was like yes i just fixed this dudes problem so i kick it again and it comes to life but the only problem is that it is wide open throttle so i wack the throttle and it settles for like two seconds and the rpms climb again. so its like 11:30 p.m. in the garage with the garage door shut and everybody else in the house has already went to bed needless to say they wern't asleep for long. so this guy that owns the bike while getting shocked removes the cap from the spark plug and heres where it gets interesting this bike was still running. so i've heard about the runaway 2 stroke,coincidently the throttle  cable was not stuck and i have attended motorcycle mechanics institute so i'm just trying to see if i'm right thinking that the problem is caused by air entering the engine from somewhere? so this guy says that the bike hasn't run right since the rebuild ya think??? can anyone help me out?     

[BDI]

I would check the flux capacider and if that seems fine then I would say a leak down test was in order. 

[BDI]

Are you sure that there are no leaks in the intake boot on either side of the carb. Are you sure the slide is dropping all the way down a two stroke engine will rev pretty high even if the throttle is only partialy open with no load. This reminds me of a funny story I will have to go post it.

[kx666]

sounds lean on the low end, what do you know about the fuel in the bike?..

but now that the motor is full of water you can do a comp. test 

[Wizzy214]

sounds like your reeds are bad.
hole in the intake boot.?

[k5abuser]

i have had this happen to me on my quadzilla . first off you have to run the carb dry to get it to stop . if you are lucky and the bike is in gear you can hold the rear brake and let the cluth out and kill it . but the best and most sure way is to kick yes KICK the carb off the bike . when it rev's like that it is refered to as desieling affect. no spark but the compression is high enough to make the fuel egnite at that rpm and keep reving . cleaning the carb then start it again . if it starts and idles ok  try to spary carb cleaner to find a leak if there are any . if there are leaks the motor will rev up . just be sure not to spray near the air box . carb cleaner with a staw tube works gr8t. good luck . but then again you might just need more hp.

[js]

I had a kdx200 climb a 100ft hill/cliff with out me. It had a crack reed.

[Hillclimb#42]

 I had this happen to me. The slide is not closed all the way. The fire doesn't clear out enough and the rings will heat up enough to keep it running. Quick check is to be sure throttle snaps back to closed position, and to be sure there is slack in cable. Otherwise the slide is hanging up in carb or idle screw turned in way too far. Something along those lines. When it happened to my k5, it melted the exaust side of piston and scored the cylinder a little. Be ready to kill the motor by putting in gear, holding the brakes and dumping the clutch in like third.           

[n2682]

i think that maybe it has a bad crank seal my reason is we were working on a really built banshee and it would run good with choke on cause it was being flooded with fuel turn the choke off it would go lean on bottom end and rev to the moon we took both spark plug wires off still ran my buddy mike is a 2 stroke god he was standing there drinkin a beer and was like bad crank seal he explained to me why this happened but i dont exactly remember what he had to say something bout crank case pressure well i replaced the seal on the mag side quad fired up never did it again? sorry im not more clear on my reasoning but if you ever meet mike he knows his stuff and will keep going and going so when he said seal i went to the cabnet and grabbed them didnt wanna hear his reason just wanted to get it done before he yelled at me for not doign what he said