KDXRIDER.NET

I put in a new weisco piston in my buddy's 01 CR250R it started right up and sounds good and seems to run good. but even with the idle turned all the way up it still won't stay ideling unless you hold the throttle a little. also when I ride it is seems to run good but not as powerful I was having a hard time getting it to pull the front wheel in 2nd gear??? We didn't do anything wrong it has good compression does anyone know what might be the problem ???

Assuming you didn't build a race bike (clearances to work with WOT right now), I'd worry less about it until you know it's broken in.

If you didn't do anything wrong...than nothing is wrong.

Sounds like carburation.....

Widen your vision some...the old 'out of the box' idea.

It doesn't have to have anything to do with something you did. It may be completely unrelated..something that was simply touched in the process....or not.

Did it sit for a long time?

Fresh gas.
Clean filter.
Clean carb.

If you can't puul the front wheel in 2nd gear on a CR250, then there IS an issue. Hopefully it's as simple as what Carvr said.

How did the bike run BEFORE the piston was replaced? Of course, this is a wierd one as a worn out 2-cycle won't idle/has no power...LOL.

My guess is all of the above. COuld be carb. Could be un-seated rings. You can feel the rings seat if you know what to feel for....Sometimes even if you don't. It CAN feel like you've doubled your HP in an instant....Not in all cases though.

I took the carb apart and cleaned the whole thing it wasn't dirty at all though, drained all the gas it has fresh gas and a new plug the filter is good, it ran strong before the piston rebuild, is it maybe just a matter of riding it for a few hours to let the motor totally break in or something (for the rings to seat?) We didn't do it wrong that is what has me stumped ????

Since it won't idle without the throttle is there by chance an air leak by the carb? Can of carb cleaner will tell all.

Did your powervalve get re-assembled correctly?

Air leaks around the carb should be checked....Even worse around the cyl base.

The powervalve is the pin that opens the little flap by the exhaust correct??? yes we put all that together right. the ideling problem was from a bad throttle cable, we fixed that but it still doesn't seem as powerful as it used to be and should be ??? will that get better with more running time to break it in or should it be powerful right after the rebuild ???

will that get better with more running time to break it in

NO!

or should it be powerful right after the rebuild ???

YES!

The piston wasnt installed backwards was it?

You are limiting a lot of possible questions/answers if the starting point is, 'We did everything right!!!!'

I'm not pinging on what you did or didn't..it's the repeated 'no offence here' that kind'a points in that direction. It's a generally true human nature kind of thing: 'NOT ME!' often exactly means exactly 'me!'

I'm just suggesting you might at least question what was done.

..before you flame Rick and all.........

How 'bout the arrow on that piston crown?

No it was installed right, we took it out today and it was better but I would say only about 92% of what it used to feel like

I've noticed that when I've changed a KTM OEM piston for a Wiesco my main jet needs to be changed.

The piston cut-away on the intake side is shaped slightly different than the Mahl OEM piston. Maybe the same thing is happening on the CR.

listen, if its your power out of the motor that is not good then if you look at the little rubber part on the right hand side of the motor and you take that off then there will be a pin which should be in a grabber, if its not in then your powervalve is not working and if its just random idleing then it might be as simple as the cable tensioner at the throttle body, if you tighten that then it will give more revs and if you loosen it then you will get less revs. not what you want.