Self Help

ENGINE WON'T START

FUEL supply problems

no gas in tank

fuel-tap (petcock) closed

defective fuel filter in tank

clogged fuel line

loose particles in tank (rust)

gas cap breather hole clogged (VERY COMMON!!!)

mixture too oil-rich (WATCH THAT DAMN RATIO!!!)

float stuck in carburetor

IGNITION (SPARK) PROBLEMS

faulty spark plug

incorrect spark plug gap

bad spark plug cap

damaged high tension wire (on external coil models)

 dirty contact breaker points

bad condenser

bad internal/external ignition coil

ignition timing incorrect

ignition kill-wire grounded

light bulb (usually rear brake) blown (applicable on certain European models, such as Vespas, Peugeots and Tomos)

fuse blown (on turn-signal models)

STARTS, BUT DOESN'T RUN WELL

COMPRESSION-RELATED PROBLEMS

loose spark plug

loose head bolts

worn gaskets (cylinder-head, cylinder base that can cause an air leak)

faulty decompressor-valve (on certain models)

broken piston rings

worn cylinder

faulty piston (NOTE: piston and cylinder should be replaced as a pair )

SYMPTOM: engine rpm doesn't increase

clutch is slipping

bad spark plug

ignition timing is incorrect

air cleaner dirty

gas cap breather hole is clogged (VERY COMMON!!!)

fuel line is dirty

bad gas/water in carburetor

exhaust clogged

SYMPTOM: engine doesn't idle or run at low rpm

worn spark plug

incorrect spark plug gap

ignition timing advanced

dirty contact breaker points

carburetor jet clogged

SYMPTOM: engine doesn't run smoothly at high rpm

bad spark plug ignition timing retarded

clogged fuel line

dirt in tank

fuel filter dirty

air cleaner/carburetor main jet clogged

choke stuck closed

faulty condenser

SYMPTOM: engine overheats

incorrect (too hot) spark plug

too lean oil-gas mixture (VERY COMMON!!!)

bad gas

incorrect ignition timing

soot in cylinder (de-carbonisation needed)

SYMPTOM: engine stops as if brakes were applied

seized piston

seized crankshaft bearings

seized gears (if applicable)

AT THIS POINT YOU ARE IN IT DEEP...YOU BETTER TURN TO HUMAN POWER AND PEDAL THE SUCKER HOME (COULD YOU DO IT WITH A HARLEY?)