Honda CRF50F 2009 Owner's Manual page 142

Specifications
Engine Specifications
Valve clearance
(cold)
Spark plug
(standard)
Spark plug
(cold climate;
below 5°C, 41°F)
Spark plug
(extended high
speed riding)
Spark plug gap
Idle speed
134
Technical Information
Intake: 0.002 in
(0.05 mm)
Exhaust: 0.002 in
(0.05 mm)
CR6HSA (NGK) or
U20FSR-U (DENSO)
CR5HSA (NGK) or
U16FSR-U (DENSO)
CR7HSA (NGK) or
U22FSR-U (DENSO)
0.024 0.028 in −
−
(0.60 0.70 mm)
±
1,700 100 rpm
Power Transmission
Primary reduction
Gear ratio, 1st
2nd
3rd
Final reduction
Final drive
4.058
3.272
1.667
1.190
2.642
chain