OK, I've had carbs rebuilt, put new fuel filter in tank, ran new oil and gas lines and made sure oil injection is working. Put in fresh prem gas also. Sprayed carbs engine fired up and died. Fuel was being pulled to carbs. Sprayed again, engine fired up and ran. Adjusted idle at 2500 rpm. Engine has 118 psi on each cyl.( I know that's low ) Both carbs are adjusted, low speed at 3/4, Main a 1 1/8. Plugs are BR9ES. Sled was running about 3-1/2 Min while I adjusted idle. Mag side spark plug was almost too hot to touch, PTO plug was just very warm. I'm guessing about 20-30 Deg difference. Is this normal or a'm I missing something? By the way this is on a 1974 GPX 338.
Yamaha Nutz
New member
Confirm ignition timing is correct for both sides (1.6mm BTDC on each side) not uncommon for the carbs to not have the same settings ...but first, have the crank seals been replaced? if not they need to be and that can be a cause to the issue you are having
Did not think of crank seals. If I remember correctly I can check seals by spraying with wd40 while engine is running and if rpm goes up then there's a leak. I don't have the tools to check the timing and dealers aren't working on sleds at this time of year.