TROUBLESHOOTING
ENGINE LACKS POWER
1. Raise wheels off ground and spin
by hand.
WHEEL SPINS FREELY
2. Check tire pressure with tire
gauge.
PRESSURE NORMAL
3. Try rapid acceleration from low to
second.
ENGINE SPEED LOWERED WHEN
CLUTCH IS RELEASED
4. Lightly accelerate engine
ENGINE SPEED INCREASES
5. Check ignition timing.
CORRECT
6. Check valve clearance.
CORRECT
7. Test cylinder compression using
compression gauge.
NORMAL
8. Check carburetor for clogging.
NOT CLOGGED
9. Remove spark plug.
NOT FOULED OR DISCOLORED
WHEEL DOES NOT SPIN FREELY-
PRESSURE TOO LOW •
ENGINE SPEED DOES NOT-
CHANGE WHEN CLUTCH IS
RELEASED
ENGINE SPEED DOES NOT-
INCREASE SUFFICIENTLY
INCORRECT.
INCORRECT.
TOO LOW
CLOGGED
FOULED OR DISCOLORED -
Probable Cause
Brake dragging
Worn or damaged wheel bearing
Wheel bearing needs lubrication
Drive chain too tight
Rear axle nut excessively tightened
•»•• Punctured tire
• Faulty tire valve
Clutch slipping
Worn clutch disc/plate
Warped clutch disc/plage
Carburetor choke closed
Clogged air cleaner
Restricted fuel flow
Clogged fuel tank breather tube
Clogged muffler
Faulty CDI unit
Faulty pulse generator
Improper valve adjustment
Worn valve seat
Valve stuck open
Worn cylinder and piston rings
Leaking head gasket
Improper valve timing
Improper valve and seat contact
Carburetor dirty or air cleaner not
serviced frequently enough
Plug not serviced frequently
enough
Use of plug with improper heat
range
21-2
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