Oct 12, 2000
well, I finally did some serious damage to my bike.... But I'm not sure what caused it... I recently replaced the #50 pilot with the stock #52 and went riding today... First I got into some deep sand and got the bike hot, (I could smell a strong odor that smelled like burning rubber or clutch and the bike was smoking alot, even after I shut it down, there was smoke coming out of the pipe for about 10 min.) I let it cool and went riding again, everything worked fine, plenty of power, although the smell was still kind of there. After riding for about 30 min., I was going though some high speed whoops in fourth, when all of a sudden the bike went wide open, independent of the throttle...... I thought the throttle was stuck, but I could move it from open to closed with no effect on the engine speed.. Well, by this time I am starting to pick up some serious speed and have no control of the bike. I was headed straight for a big pile of rocks so I bailed off the back, the bike was still wide open.

I did many cartwheels and flips while bouncing off the ground every 10 feet.. Im sure the bike did the same.

I got lucky with just a twisted ankle and an assortment of cuts and bruises. The bike suffered a bent subframe (kinda bad), smashed pipe, and the motor won't start, feels like it has less compression, sounds different when I kick it over.

My question is this: what the hell happend? it ran fine before. The only thing I did was change the pilot (richer). I'm thinking It may be an air leak, but it came on all of a sudden, and what was that smell and why was the exaust smoking after I turned it off?

How much is a new subframe? Can it be straightend?

I had my gas mixed at 40:1 with mobile premix...



Jan 27, 2001
I think your bike ran out of fuel, thats why it went wide open without control. It's sort of running your bike on nitrous, as it runs super lean, and making unbelievable horsepower. The smoke and smell is probably the unburnt oil in your silencer burning from the heat because of the engine working so hard in the sand. My 80' rm125 does that when i do long hill climbs (1st gear wide open).

just my $.02


May 20, 2001
Originally posted by KX'er
My question is this: what the hell happend? it ran fine before. The only thing I did was change the pilot (richer). I'm thinking It may be an air leak, but it came on all of a sudden, and what was that smell and why was the exaust smoking after I turned it off?

I'm still thinking stuck throttle, and do think that the smoke was from unburnt stuff in the pipe/silencer. I may be possible to still move the throttle grip even if the slide in the carb doesn't move.

Maybe the throttle cable got pinched somehow when you changed your jetting? At least on those carbs where you twist the whole top part to attach it you can twist it too hard and have the cable pinch at WFO (happened to my dad on his CR5)


Jan 14, 2000
Stuck throttle

After youv'e had it happen a few time you learn to expect it:scream: Mine was caused be dirt in the carb. It goes up th main jet and jams the needle, so it will not close, usually on very bumpy terrain (the carb get really shaken up). The only way to clear it is to pull in the clutch and rev it out, this is easlier said that done when in 4th and completely out of control, and your brain / hand co-ordination says NO WAY!!.

There are two ways dirt / sand can get in the bowl, first from the gas itself, check the petcock filter, and second, up the vent hoses. I had a broken vent hose that stuck out above the chain and the dirt would be thrown up the vent be the chain.

Nothing gets you up a rutted bumped out hill like a stuck throttle:confused: :p


Aug 13, 2000
I have had the slide stick in the open position a couple of times. Once it was due to dirt and a weak return spring.

I have always used the kill button to stop a runaway engine. This seems to be the safest method of regaining control. I even milked a bike home using the kill button once.

It' s kinda like those WWI aircraft, some of them were always at full throttle and the ignition switch was used to control the power. That's why the old movies had the aircraft sounding like they were going to die any second, the pilot was just turning off the ignition to reduce power for landing.

Remember the kill switch and clutch.



Apprentice Goon
Mar 16, 2001
Charlestown, IN
Make certain your spring retainer is seated properly each time you fiddle with the carb.

Man, what a place for that to happen....4th in the whoops! :scream:


Mar 7, 2001
Did it happen too fast to think about using the clutch and kill switch? Or, like several people I know, have you disconnected the kill switch? I know on my racing quad I had a teathered kill switch so if I fell off it would quit. I have thought about adding one to my bike. Not sure if it would be practical.


Oct 12, 2000
Even if I had hit the kill switch, I would have had to bail, I was headed straight for a bunch of rocks, which I hit anyway, but didn't want to be tangling with the bike through the whole deal...

There didn't look like there was any dirt in the carb or airbox... I'm going to take the top end apart tomorrow...

The subframe is tweaked pretty bad, beyond repair, anyone know how much they cost?

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