Yamaha RD250 Owner's Manual page 88

result; also, carbon will f o r m on the exposed
threads resulting in combustion Chamber hot
spots and thread damage. A l w a y s use a spark
plug with the proper reach.
Spark plug reach: 19.0 m m
Before installing any spark plug, measure the
electrode gap with a wire thickness gauge
and adjust to specification.
Spark plug gap: 0.6 ~ 0.7 mm
When installing the plug, always clean the gas-
ket surface. Wipe off any grime f r o m the
threads and torque the spark plug properly.
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