Hi all...i recently rebuilt my 1950 ZM21. I made a barrel casket, however after putting the bike back together and running it I remembered I forgot one hole in the barrel casket. The hole sits behind the tappets and barrel bolt holes. from the parts manual I can't see any reason why I would need a hole in the casket as the barrel sits over the hole. My question is do I have to pull the bike apart and remake a casket or just leave it as is? The bike sounds more rattly than normal and the spake plug is dry.

Assuming we are referring to the same hole, I'd always thought of that one as being for oil to drain back down to the crankcase from the tappet chest. But I suppose it could also serve to allow some 'splash' up to the same area? The hole is not blocked off by the barrel. There are the bolts holes, a locating dowel and this 'oil hole'. Maybe, just maybe, it might be possible to use a scalpel to carefully cut a hole through, use a piece of rod with a dab of grease on the end to catch the piece you cut out? Or take it off and do it again. I wouldn't leave it, it is there for a reason, blanking it off wont be good news.

Crankcase pressure forces an oil mist up though this hole when the engine is running to lubricate the tappet heads and valve stems...and oil will drain the other way to a degree when the engine is stationary...It is important that this hole is not blocked by the gasket...Ian

email (option): ian@wright52.plus.com