U.M.R. Engines

RINGS - CRACKED / BROKEN
First and second compression rings commonly break causing low compression and misfiring. The main cause of compression rings being cracked and broken is that the engine was being driven under detonation/ conditions.

This dangerous condition is present and made evident by engine pinging. Even slight pinging over a long period will eventually result in ring damage. This condition is usually present when the ignition timing is too advanced (base intermediate or total) or the fuel is of too low an octane rating to suit the compression ratio. Severe detonation can exist if engine is run overloaded or at high temperatures.

Detonation will also damage and crack the piston ring groves and piston crown. Most engine components will sustain damage if an engine is run while pinging is evident.

Another cause of broken rings is excessive side wear. This side wear is usually the result of abrasive contamination. Incorrect assembly of rings into bores is another common cause. (Compression problem exists at initial start up.)

Another common cause is insufficient ring end gap when assembled. (Assembly fault) Engine overheating or incorrect rings fitted (wrong radial depth or material choice) can also be the primary cause.

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