GENERAL INFORMATION
Page 1C-10 90-857138R1 MAY 2000
Compression Check
1. Remove spark plugs.
2. Install compression gauge in spark plug hole.
3. Hold throttle plate at W.O.T.
4. Crank the engine over until the compression reading peaks on the gauge. Record the
reading.
5. Check and record compression of cylinder. A reading below 36 psi might indicate a total
engine wear problem.
Maximum (psi)* Minimum (psi)*
50 36
*Compression listed above is with decompression assembly in operation.
Maximum (psi)* Minimum (psi)*
130 100
*Compression listed above is with decompression assembly not in operation. (Rocker arm
on exhaust side is removed)
6. Compression check is important because an engine with low compression cannot be
tuned successfully to give peak performance. It is essential, therefore, that improper
compression be corrected before proceeding with an engine tuneup.
7. Cylinder scoring: If powerhead shows any indication of overheating, such as discolored
or scorched paint, visually inspect cylinder for scoring or other damage as outlined in
Section 4 “Powerhead.”
To Next Page
Loading...
Need help?
General
