Mid 1950s AMC 500 single engine, some oil smoke from exhaust

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Dibnah
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Mid 1950s AMC 500 single engine, some oil smoke from exhaust

Post by Dibnah »

Greetings All,

No oil smoke visible in the mirror when progressing, no oil smoke visible immediately after stopping (with hot engine idling), some puffs of oil smoke from the exhaust if idling continues for more than a couple of minutes e.g. local railway level crossing. Oil tank does not need topping up between oil changes (approx 1000miles), spark plug can get a bit "crusty" , which suggests burning oil, but the plug is changed every year so the crustyness doesn't appear to affect engine operation.

Crankcase breather is clear.
Oil return to tank looks OK.
Bike starts and runs well (first kick this morning, with an audience)

Not a big problem in the general scheme of things, although annoying. I plan to look at the easy solutions to start with:

Adjustable oil feed screw for the inlet valve guide (several useful posts on here, thanks)
Oil feed for the exhaust valve guide (several useful posts on here, thanks)
I currently use 20w50, I might try straight 50 as an experiment

Any suggestions to add to the list gratefully received !
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ajscomboman
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Re: Mid 1950s AMC 500 single engine, some oil smoke from exhaust

Post by ajscomboman »

Sounds like valve guides are bit worn, it's a classic sign. Nothing on the move or brief blips, sit at traffic lights idling and pull away you then get a brief puff of oil smoke.
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Dibnah
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Re: Mid 1950s AMC 500 single engine, some oil smoke from exhaust

Post by Dibnah »

Thanks AJScomboman, it could certainly be worn valve guides, but wouldn't the smoke be visible as soon as I stop the bike and allow the engine to idle? I probably need to arrange for someone to follow me to see if the bike smokes on the overrun and when accelerating.
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Dibnah
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Re: Mid 1950s AMC 500 single engine, some oil smoke from exhaust

Post by Dibnah »

OIl change, I've replaced the 20w50 with straight 40, but still some oil smoke when idling. Some bronze observed in the used engine oil, so there might be a problem! I'll post a separate thread.
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