i have a 92 lt80,just rebuilt top end(new cylinder/piston),brand new carb(OEM),new reed(OEM),new petcock(yamaha warrior to eliminate vacuum on carb),new starter,clear fueline. it will run for a few minutes then shut off. wont restart unless it sets for awhile or i empty carb. i have another lt80 that i did exact same changes to and it runs like a champ. i'm running out of idea's. got any? willing to try anything!

 

"wont restart unless it sets for awhile or i empty carb"
Hmm. Ok, When this happens, are you riding it along or sitting and idleing?
When it shuts off, is the plug wet (flooded)? What does applying the throttle do to it when it's quiting (spit/sputter/bog)? When it quits and you try to restart, the motor does spin over, right?
Well I guess we should do something, right or wrong.
I'd swap out the coil/CDI from the running machine. That should eliminate that aspect.
After that, the carb.
Let's go from there.