Ignition system
- Improper spark plug gap
- Improper spark plug heat range
- Faulty ignitor unit
Fuel system
- Improper carburetor main jet setting
- Improper fuel level
- Clogged air filter element
Compression system
- Heavy carbon build-up
Engine oil
- Improper oil level
- Improper oil viscosity
- Inferior oil quality
Brake
- Brake drag