81 kdx250 no bottom end power

[aviatre]

I have a 1981 KDX250. I have had it since new. it only has 980 miles on it. It used to have gobs of low end power. I have cleaned the carb, I have even flushed the muffler with solvent to make sure that it isn't clogged. I just re-ringed it. and it still stutters badly until the rpm comes up. Any help is appreciated.

[dfeckel]

Did it sit for a long time with fuel in the carb? If so, there may be some clogged passages in the body of the carb that a simple cleaning might not get. An ultrasonic cleaning, if you can swing it, is great at removing clogs like that.

It might be a good idea to do a compression check.

Play with the needle clip a notch in each direction and see if any better.

How's your spark?

Is the bike hard to start at all?

Did the piston go in backwards when you redid the ring?

Show some pics!

[jgas]

My newly rebuilt 79 has good low end, my 81, also with a new motor but a large scratch in the cylinder has poor low end, but which shouldn't hurt power too much as it is more scratched at an angle rather than straight up and down. I think it's losing a little compression but not much. The 81 is actually a little harder to kick than the 79. has poor low end. I suspect bad reeds in the 81, as well as poor jetting. Both of my early DXs rev very slowly. I have read that they have heavier cranks than the KXs, and do have heavier flywheels. The KX flywheel will fit your bike and will not give more low end, but will make it rev quicker, transitioning "on to the pipe". Something to check is for a plugged up/overly oily silencer which can kill low end.