I have a 2000 Yamaha 500 VMAX that starts and runs with no problems whatsoever, except for after the engine warms up. The longer I ride the blacker the exhaust gets. When I stop, the machine leaves a large black spot in the snow where the exhaust is coming out. The engine will also cuts itself back to a maximum of 5500 RPM and I'm having to limp myself back to the truck.
I took the carbs apart and soaked the parts in cleaner and made sure the pilot screw was set to what the owner's manual recommends (1 3/4 turns back from tight) and I still am ending up with oil coated spark plugs.
Being completely ignorant on this, can someone recommend my next step of action? I'm guessing I just need to play with the pilot screw setting but I have no idea of how far to adjust it (1/4 turn, 1/2 turn, etc.).
I've verified that the choke isn't getting stuck open and that the oil pump cable is adjusted per the owner's manual.
My typical riding area is sea level to less than 1,000 ft.