The old 350 is acting up again. Breaking up/dying and occasionally backfiring at beginning of throttle. Spark plug a little on the white side. I’ve pulled the carb and ensured the pilot jet is clear. I’ve replaced fuel line from tank to carb. I’ve cleaned contacts on coil and checked spark. I’ve moved needle clip position from middle slot down one slot. I’ve cleaned entire carb. I’ve brought air screw from 2 to 2 1/2 turns out. Checked intake boot for leaks. Original carb with stock jetting. Awaiting arrival of #45 pilot jet to replace original #42 pilot to see if that helps. Anyone have any further insight or suggestions? Will also occasionally just die out of the blue while at idle after having run for several minutes.

 

All sorts of things can cause a misfire. Try a new plug first, and check that the voltage reg is not producing more than 15v when running. I then go for carb cleaning, followed by a new coil, then CDI but I have both in stock, for non dealers, substitution starts getting expensive. Had a 300 with this problem last week, tried the above with no improvement so went for a new trigger coil (far easier to fit on a 300 than a 350), this seems to have cured it. The new RM stator trigger coil was a pile of poo too, hit the flywheel when I tried to start it. Had to file almost 1mm off to get the right air gap. Luckily 300s are about the only bike that you can check the air gap on.