Check Of Compression Pressure - Yamaha YBR 125 Service Manual

When compression pressure
A Poor air valve contact will cause compression
leakage.
B Adjustment of air valve clearance is poor
C Piston,cylinder and piston ring will be worn out
When compression pressure is too high
A The burning room of cylinder head will have
carbon deposit
B Piston head will have carbon deposit

Check of compression pressure

Note:
Insufficient compression pressure wil result in the
performance loss.
1. Check:
Air valve clearance→adjust
Refter to "adjustment of air valve"
2. Start and warm the engine for several minutes.
3. Stop the engine
4. Remove:spark plug
5. Install:
Pressure manometer
Joint
6.Check
Compression pressure
Measurement steps:
Crank over the engine with the electric starter or kick
starter with the throttle wide-open until the compression
reading on the manoeter reach to the max.value,then
read the max. one.
Check readings with specified levels.
7. Install:
Spark plug,spark plug cap
3 - 10
Pressure manometer:90890-03081
Joint:90890-04082
Standard compression pressure:
1200KPa( 12kg/cm)
3
INSP
ADJ
2