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KX 100 help???

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Just got a KX100 (2002) for my son. the bike it in excellent condition but seems to be down on power. A CR85 consistantly outruns him in a 400 foot drag by a three or four bike length, and the bike will not lift the front end by just rolling on the throttle, very little wheelspin/roost.

I've checked the following, air filter, silencer (repacked), powervalve is working properly, no exhaust leaks.

The bike runs fine, starts fine, sounds fine, but just seems slow.

Could compression be down and possibly causing this? Would everything else seem normal if compression was down and needing a topend?

Thanks for your help.

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Because he is loosing in drag races doesn't mean the bike is down on power.

Low compression would cause loss in power, have you tested it? Does it take alot of kicks to start?

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it does take several kicks to get it going, and it won't idle. Even when it's warm it takes several kicks to get it running....

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Worn top-end, and jetting issues.

Those bikes are often ridden by young kids with fathers that don't ride, and refuse to spend money for a new top-end because "It's still running fine". But those top-ends wear fast due to very high revs. After 30-40 hours, those bikes can easily be down several horsepower from new. A fresh, properly tuned KX100 will nearly run with 125s, it shouldn't get out-dragged by an 85 if the rider knows how to ride.

The stock jetting is poor, especially the pilot circuit. They are too rich at sea level. If you are more than 1500 feet or so above sea level, it's way too rich.

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I have a KX100 and i'm riding about 2300ft and higher and one thing I noticed is that when you get higher it boggs a little bit so I rejetted it and it runs perfect now.

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You probably need a top end since it takes more than one good kick to fire up and since it is down on power, I noticed a huge difference when I got a new piston and rings and a cylinder replate on my 250.

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I'm gonna agree with everyone else as your own interpretation. Top end, definately. A good 2 stroke should start 1st or 2nd kick. My sons is taking 4-5 kicks and his topend is down to 125psi on a compression check. But i've been procrastinating.

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