16 replies to this topic

[Yoda]

I agree, but in my experience it helps to seat and seal the rings too. a polished set of rings and bore can allow oil past, but you would usually see smoke all the time, If its only smoking on the overun, i would expect the problem is more likely to be valve guides. There is also the thought in my head that if the cankcase is over pressurising for any reason, then the pcv could be pushing oil up to the carb if the breathers are fitted. this can also happen if the valve gaps are too tight. Might be worth seeing if the air filter or carb mouth has any evidence of oil.

[tiger99]

Synthetic oil is totally unsuitable for a Mini anyway, as it does not cope well with the gearbox. For the same reason, it may not be advisable to use special running-in oil, which does exist, unless it is also approved for gearbox use.

If it is ring leakage, a strip down and light hone, maybe even just glaze busting with abrasive paper, followed by another running-in cycle, might do the trick. New rings may not be necessary. The problem is usually caused by inital glazing of the bores, which then prevents the rings bedding in.