Carburetor
- Improperly returned starter plunger
- Loose pilot jet
- Clogged pilot air jet
- Improperly synchronized carburetors
- Improperly adjusted idle speed
- (throttle stop screw)
- Improper throttle cable free play
- Flooded carburetor
Electrical system
- Faulty battery
- Faulty spark plug
- Faulty ignitor unit
- Faulty pickup coil
- Faulty ignition coil
Valve train
- Improperly adjusted valve clearance
Air filter
- Clogged air filter element