I'm hoping someone can help me with this problem. I have a '99 AC 300 4X4 and it runs rough and cuts out and backfires after reaching full operating temp. I have cleaned the carb twice, had a new regulator/rectifier installed, and ran about a half can of Sea Foam through it. The thing runs fine until it warms up. I think I read here a while back that valve adjustment will cause these symptoms. Anyone got a clue? It actually was idling extremely rough before the Sea Foam and now idle isn't a problem. Thanks, Mike

 

Mine had a similar problem once and what i found was a hole in one of the vac. lines running from the fuel pump to the intake boot after the carb. Not real sure how yours is set up, but it is worth looking into. It was causing the fuel pump to operate very weak and also allowing air into the intake causing a very lean mixture. It to cut out and popped after warming up.

 

I'm not 100% sure, but I don't think I have a fuel pump. I believe it is just gravity flow from tank to carb??