Help, no low end power!

[Kasjok]

I have CR250 -01 which I changed the top end. Now it doesn`t have almost no power with low RPMs, and i mean like realy low RPMs. It`s a BLAST if I reach like 1/5 of throttle, but before that there`s no power to be found :(
Before it had atleast decent power with low RPMs. I had a wiseco piston before and now I installed a Prox piston. Could it be because of different piston or do I just need to fine tune my carburator again? Or is there something third? Please help me! Thanks

 

[toddb3]

I'm not sure but I think the Wiseco kits have a little more compression than other pistons, that may be the loss of low-end that youre feeling.

 

[Kasjok]

That can`t be, because the old piston was so wore out that by slightly pressing kickstarter, the kickstarter went to the bottom. Now with new piston it`s very hard to even move the kickstarter.

 

[darringer]

Make sure your powervalve is working. When you slide the cylinder on the cases, the linkage rod in the cylinder must mate with the linkage in the case for the powervalve to work properly. Remove the 17mm bolt on the cylinder (On the ignition side). Start the bike and rev it up to see if the powervalve is moving. It should move 90 deg. or so.

 

[Kasjok]

I will try this one, but tell me is it possible that different pistons need different jeting?

 

[RM_guy]

You don't need to re-jet with a different piston. As far as your low end power, check to make sure the reeds are in good shape. Poor starting is another sign of bad reeds. The power valve (if it is not opening) will only kill the top end power, not the low end. But you should make sure that it isn't stuck wide open. That would hurt low end poser.

 

[Kasjok]

Starting is always very good. It starts first kick even if has been in garage for 2 weeks. But i will check out the reeds, as i have never checked them on this bike.

 

[dirt bike dave]

If the power valve is stuck open, it most certainly will kill the bottom end power.

Check the powervalve operation as Darringer instructed. All you have to do is remove the inspection cover (one 17 mm head) on the left side of the cylinder, start the bike and rev it up. Have you done that yet?

If the end of the shaft does not rotate from the closed position to the open position as revs rise, you did not properly line up the linkage to the powervalve when you put the cylinder back on. This is a very easy mistake to make on your generation CR250.

If the powervalve is stuck open you will need to lift the cylinder from the crankcase and try again to line up the linkage properly.

 

[Kasjok]

Doesn`t matter any more, just got it sold! :nod:

I am planing to go for 450 4 stroke, is there any brands which I should prefer in 2003-2004? And yes I know I am making offtopic, but I think it`s so quick question that I won`t make a new thread! Thanks

 

[sick 96 250]

You don't need to re-jet with a different piston. As far as your low end power, check to make sure the reeds are in good shape. Poor starting is another sign of bad reeds. The power valve (if it is not opening) will only kill the top end power, not the low end. But you should make sure that it isn't stuck wide open. That would hurt low end poser.

it could be possible it needs a re-jet if you messed with it while his last top end was going out. I normally have to re-jet if i dont do the top end right away and tune a little for it while its getting worn out. But I would def check the reeds like mentioned. Did you disasemble the power valve while you had everything apart? That could need adjusted maybe.

 

[Kasjok]

I think it`s most likely that I messed up the power rod.