Compression Test and Plug Inspection

Mileage: 29,424

Maintenance Summary:

  • Performed Compression Test (engine slightly warm):
    • Left: 158 psi
    • Right: 160 psi
    • Spec: 171 +/- 20 psi

Some time ago I borrowed a plug adapter from a friend so that I could perform a compression test; my compression gauge didn’t have an adapter that matched the plug size for this bike.  As I’ve had the borrowed adapter in my possession far too long, today’s task is to perform a compression test so that I can reunite the adapter with its owner.

The only reason for performing this test is regular maintenance.   I’ve no reason to suspect that anything is wrong with the bike.

I only warmed the engine up on idle for a few minutes.  The cylinders were warm, but not hot.

This isn’t an expensive gauge, so I don’t know how accurate it is.   At 90 psi, it reads about 5 psi lower than another cheap gauge I have on my air compressor.  Still the compression readings are well within spec, and very well balanced — the most important thing.  Even a cheap gauge can be used to check if one cylinder has lower pressure than the other.

Right Cylinder @ 160 psi
Left Cylinder @ 158 psi

The plugs look good, especially considering that I pulled them after a few minutes of warming the bike from cold with the choke on.  I would have preferred to look at these after a good run, but it’s cold and wet outside.

Left and Right plugs

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