KXR80 conversion bike

I am in the middle of building a little thumper for my 11 year old. Took a '79 XR80 driveline and put it into a '85 KX80 chassis. Fairly straight forward build with nothing too wierd going on, until I tried to get it running. I had to build a straight intake to clear things and keep the carb from tipping towards the rear. 


We rebuild the top end with a new Wiseco piston (48.5mm). Set the timing to factory and got it to idle. Then the trouble started.


1. When tipping the throttle in to anything that is "off idle" the bike dies.

2. took it to the local mechanic thinking I did something wrong on the rebuild.

    a. $80 bucks later it idles like a champ. Still can't ride it. Swaped out everything: flywheel, intake, carb (new), all of the ignition, even the keyway. Same problem everytime. Idle is fine, but tip in the throttle and it dies.

3. Now it looks like a tear down again.


The mechanic did get the idle spot on. I'm leaning towards the timing chain being off by a tooth for timing. The tip in is acting odd. It bucks & pops like a miss, so I guess it doesn't totally die out anymore.


Any ideas I have not tried yet????



Edited by GSjimmy

My 04 crf 250 r has an idle that's high then just stalls its cause timings off by one tooth. It'll also run a little hotter


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