Primary case alternator cable exit hole

On my slimline 99 with original cases the cable hole is about 3/8th dia and only just clears the top chain run (all from memory).

Hi Tony,

I am just finishing a complete rebuild of my 1957 99 and drilled out my rivets too, just so that the rear case could be painted properly. I fitted the felt seals, as on the footrest tunnel, on rebuilding as an extra precaution against leaking oil.

Regards

Dick 

Hopefully Phil will turn up with something on the chaincase hole.  I thought they made a change from the top edge (where mine is, and as Robert says his is) to a lower location to reduce the chance of the chain cutting the cable.  In which case, both are 'correct'.

On the matter of felt seals - there was talk some time ago on the 'singles' pages about a felt seal around between the magneto and magneto chain case, and how it is sometimes present and sometimes not.  But I've been browsing Phil Vincent's 'Tuning for Speed' and in one passage he recommends owners to add such a seal.  Not to keep oil in (it's a Norton - that would be an absurd objective) but to keep abrasive dirt out.  Especially if riding off road or sand racing.  Anyway, what he's written suggests that seals weren't necessarily in the parts list because it was often left to the owner to add them if he wanted to!  Maybe someone can add something?

It seems to be a reminder that just because a felt seal isn't much good at retaining lubricant, it does not follow that it's not worth having.

The only oil that could exit the case at that point will be that which is thrown up by the chain and runs down the back of the case onto the gearbox shaft. I formed a half circle bead of bath mastic on the inner case and "veed" it with a pen knife to drain this oil away from the shaft. Along with case straightening (ala Hudsons script) ,trimming outer case to clear the prop stand mount,"O" ring on the inspection cap,mastic on the footrest shaft rubber, and a coating of Red Rubber grease on the band seal, I can go many months with no top up and no drips under the bike when "up the café". Bliss!!.