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hey guys i got a 1986 kdx 200 off road only kdx 200 about 6 months ago.
i did a top end rebuild, put on a dg powere pipe, power core 2 muffler, boyesen reeds and sandblasted and painted frame and painted everything, looks smick, but problem is it doesnt run too good. it starts first kick but i apply full throttle in any gear and it only revs to about half rpm and wont go anymore, it is very gutless and sound like it is pinging or something. i tried new spark plug, air filter is crystal clean, got a great fuel mixture. i played with the level of the main needle this does nothing. any ideas what could be wrong?

Plugged silencer? Wrong jetting / dirty carb?

You didn't mention whether it ran well before you pulled it apart or not. If it did, look at the changes you made and maybe swap the old pipe and silencer back on to see if that has any effect.

Otherwise, check the timing and then check the coil output

Does it make full rpms when not under load?

You say the mixture is good, but you can't really tell if you're only making partial power. Check the jets (main and pilot) to see if they are at least in the right ball park. Check both for any obstructions.

Check the airbox and boot for any obstructions or leakage. I have a yz80 that wouldn't get on the pipe because of a leaky seal between the carb and airbox.

Do you have the correct ring gap? If its too tight it may be putting too much resistance on the bore. Check the compression to make sure your head gasket isn't leaking.

At least that's where I'd start.

Good luck

it ran well before i pulled it apart, although it had a broken power valve lever but it still hit power band somewhat. and it does seem to rev responsively and highly when not under load. thanks buddy ill check all that stuff after work