Tacho Drive

[Saltydog42]

I have a super rocket with the taco drive from the oil pump and housing on inner timing cover.
On removing the drive at the instrument  there seemed to be a lot of oil driven up the cable and i am worried about this getting into the instrument as rebuilds aint cheap.
On stripping down the drive unit I notice that the sleeve on the drive shaft is an easy slide fit in the timing cover - is this correct as there seems to be a lot of oil coming up the outside of the sleeve and i am concerned that both shaft and sleeve are rotating in the case. Any help would be appreciated.
On the same subject there is an O ring but I don't see any obvious place for it to fit - is it on the outer end of the shaft where the shaft fits into the outer cover. I have not been able to find diagram of the assembly, just an early parts diagram which does not help and has part numbers no longer recognised
Thanks
Barry

[JulianS]

The original BSA made drive had a scroll and a rather flimsy O ring to seal it. Some were made with scroll one way and some with reversed scroll and some with no scroll. Problems with a leak here are documented in the service bulletins. First and second photos shows genuine BSA A10 parts. Note no recess in housing for O ring, pattern ones do have a recess.

The common pattern ones have neither scroll nor O ring. Third photo

The housing for the A65 type housing (which also fits the A10) is machined to take a much more substantial O ring which is more successful at keeping the oil out of the cable. The pattern ones have a larger machine aperture than the original and it can be a struggle to find a snug fitting O ring.

So best bet go for the A65 housing and O ring.

[JulianS]

Here are some early 1060s USA service bulletins about the leak.

[Saltydog42]

Thanks Guys - very informative , I have ordered new assembly which is listed for A10 /A65 and wil see what that looks like when it arrives.
Any thoughts on the fit of sleeve in the timing case, should it be a easy push fit or a press fit?