Classic Cycles Technical Resources
73
B. BURNED PLUG
• Check spark with gap tester.
WEAK SPARK
(Not likely)
GOOD SPARK
(1) TIMING
(a) Advanced
(2) FUEL SYSTEM
(a) Insufficient Oil
(b) Incorrect oil pump adjustment
(3) CARBURETION
(a) Jets or passages plugged
(b) Jet needle adjustment
(c) Incorrect main jet
(4) COMPRESSION
(a) Cylinder packing
(b) Crankcase packing
(c) Crankcase drain
(d) Magneto side oil seal
(5) MILLED HEAD
(6) CARBON FOULING
(a) Cylinder head — pre-ignition
(b) Excessive compression
C. FOULED PLUG
• Check spark with gap tester
WEAK SPARK
(1) IGNITION
(a) Burned points
(b) Point gap wrong
(c) Condenser bad
(d) Coil defective
GOOD SPARK
(1) FUEL
(a) Mixture too rich
(b) Too much oil from pump
(2) AIR CLEANER
(a) Plugged
(b) Not installed
(3) CARBURETION
(a) Float level
(b) Jet needle adjustment
(c) Main jet
(4) COMPRESSION
(a) Rings worn
(b) Piston worn
(c) Cylinder worn
(d) Head gasket leak
(e) Stuck rings
(f) Scoring
(g) "O" ring leak
(h) Rotary valve oil seal leak
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