The A, B, C, ... refers to the interchangeability table; see here:



When I faced a similar head stock bearing problem with my F28 (600EW), I was able to use a pair of slimmer taper roller bearings. To make up the difference, adapters were turned on the lathe. I think I only needed an adapter for the outer race diameter and height. I did a similar thing for my Birmingham Scott that had indented races. But there I was changing from loose ball to a taper roller bearing. The size was more of a challenge but I was able to use special taper roller bearings made to convert older BMW twins. Even so, adapters needed to be made, which were made to look like the old ball races and disguise the modification.

-Doug

My recently acquired T6 has headstock bearings that are very "notchy" and steering feels awful and dangerous.

Having dismantled the headstock, I see they are taper rollers with an OD of 54mm and an ID of 27mm; (width about 16mm);  they also have some very heavy grooves in the shells which are the cause of the terrible steering.

According to my bearing catalogues, this seems to be a non-standard size, so what have other owners done?  Is it a case of sleeving / grinding a standard taper roller bearing, and if so, which one?  Or has the club had any made?

While I'm posting, my parts list seems to be missing the first few pages, so I'm having problems working out what "A", "B" and "C" means in the column just before the price column.

Thanks for any help.

For Sale
Dragonfly crankshaft. Stripped and cleaned,centre section
re-assembled,Good journals,New big end rollers. Problem - only one bigend roller cage. Hence £320 including U.K.Postage. EMail me (N.C.R. May/June page36)
Neville

Yes Dave,
                 The thread is 1/8"BSP - that is .383"dia x 28 tpi. If you need a new plug, they are available from plumbers merchants, but need the flange turned down so that it just clears the bottom of the gearbox side cover.
  Hope this helps,
                            Regards,
                                           Eddie.

Has anyone got any of the following please?
 
They are for a 600 but I think the smaller capacity models shared the same parts, and different earlier 30's bikes used the BTH Ammeter.

Primary drive rear cush hub assembly & associated sprocket.
Primary drive outer cover.
BTH Ammeter.

Condition unimportant.