my new to me 2001 WR 426 is having troubles. it runs fine when trundling down the road with the throttle just cracked but it won't idle and the with throttle anywhere between 1/4 and 3/4 it pops splutters and make very little power. the way the bike runs is very dependent on throttle position. if i ride the bike really hard and just open it up it runs the way it should and i have to keep my eye on the front wheel to make sure its not up in the air. I have been through the carby very thoroughly at least three times and i know carbs fairly well so unless there is something particularly obscure that i could have missed i can't see there being any other issues with the carby. the plug is black and sooty every time i check it but no amount of leaning the mixture is stopping my problems. I got hold of a CDI unit from an 03 WR450 which i could try but i am wondering if it compatible. i can't afford fry this CDI. I also have a the carb from the 450 which i could try but yhis would requite quite a bit of fiddling to make it work. Does this sound to you like an ignition problem and can i try the other CDI? or if it doesn't where should i go next. P.S valve clearances are within spec and everything's fine under the tappet cover.