Cylinder Head. Compression Measurement

Compression Measurement

• Remove:

Side Covers (see Side Cover Removal in the Frame

chapter)

Lower Fairings (see Lower Fairing Removal in the Frame

chapter)

Seat (see Seat Removal in the Frame chapter)

• Thoroughly warm up the engine so that the engine oil be­tween the piston and cylinder wall will help seal compres­sion as it does during normal running.

• Stop the engine, remove the fuel tank, ignition coil and spark plugs, and attach the compression gauge firmly into the spark plug hole.

Special Tools - Compression Gauge, 20 kgf/cm²: 57001-221 [A] Compression Gauge Adapter, M12 × 1.25: 57001-1644 [B]

• Measure the cylinder compression. • Using the starter motor, turn the engine over with the throt­tle fully open until the compression gauge stops rising; the compression is the highest reading obtainable. NOTE ○Be sure the battery is fully charged. ○Be sure no air leaks out of the cylinder head gasket.

Cylinder Compression (Usable Range) 960 ~ 1 470 kPa (9.8 ~ 15.0 kgf/cm²,139-213 psi) @410 r/min (rpm)

• Repeat the measurement for the other cylinder.

• If cylinder compression is higher than the usable range, check the following:

1. Carbon build-up on the piston head and cylinder head. - clean off any carbon on the piston head and cylinder head.

2. Cylinder head gasket, cylinder base gasket - use only the proper gaskets for the cylinder head and base. The use of gaskets of the incorrect thickness will change the compression.

3. Valve stem oil seals and piston rings - rapid carbon accumulation in the combustion chambers may be caused by damaged valve stem oil seals and/or dam­aged piston oil rings. This may be indicated by white exhaust smoke.