See Figure 1
A noticeable lack of engine power, excessive oil consumption and/or poor fuel mileage measured over an extended period are all indicators of internal engine wear. Worn piston rings, scored or worn cylinder bores, blown head gaskets, sticking or burnt valves and worn valve seats are all possible culprits here. A check of each cylinder's compression will help you locate the problems.
As mentioned in the tools and equipment of portion General Information & Maintenance , a screw-in type compression gauge is more accurate than the type you simply hold against the spark plug hole, although it takes slightly longer to use. It's worth it to obtain a more accurate reading. Follow these procedures:
- Warm up the engine to normal operating temperature.
- Remove all the spark plugs.
- Disconnect the high tension lead from the ignition coil.
- Fully open the throttle either by operating the carburetor throttle linkage by hand or by having an assistant floor the accelerator pedal.
- Screw the compression gauge into the No. 1 spark plug hole until the fitting is snug.