- This is the very important twin row, self centering bearing that was originally fitted in both top and bottom bevel housings in all International and early Manx engines. They are self centering, because they allow for the vertical shaft to be moved off centre slightly, and therefore it facilitates the cambox being 'swivelled' out from under the top frame tube, when working on the engine. It also allows for any small discrepancy in the cambox being out of line with the bottom bearing housing.
Unfortunately the original type Twin row self centering bronze caged ball bearing has been obsolete for many years and is no longer available (it was originally made by Hoffman, who later became RHP - the top brand, in the photographs you will see this bearing was supplied in the 1960's/70's yellow RHP box's - with them wrapped in the original heavy grease paper in rolls of 5 bearings - 4 rolls per box).
Because they have not been available for many years, whatever stock is still out there is hideously expensive to obtain - and the bearing suppliers know this! For the top bevel housing, it is possible to use a single row 'none self centering' replacement of the same dimensions, which I can also supply (see Item 0006), however, it is really important that the correct twin row bearing is used on at least the bottom housing . . . failure to do this could mean you canot remove the cambox with the engine fitted in the frame! And if you can afford it, it is best to go for this bearing top and bottom.
LATEST UPDATE 12/03/16: Again, I have managed to obtain another batch of these - but to give some visiblity, I was quoted £93 trade by one specialist supplier, thats how rare they have now become! (needless to say I was finally able to get some at a better rate - otherwise I would not be in business or they would not be the price I quote here!) This latest batch is exactly as the last - brand new original RHP - split out from the orginal box of 40 RHP bearings and supplied individually in two plastic bags to protect them and keep them in line. I know RHP have no intention to make these again and dont think anyone can justify having a large enough batch made to warrant the cost - so once they are gone they are gone! I have tried to keep the cost almost the same as the previoius 2014 batch.
Final hint on fitting these bearings (because at the cost of them you dont want to waste them!!): I have fitted these bearings into housings many times over the years and I have found it is very important not to knock the inner bearing, or accidentally press it excessively, so that the inner race pushes 'out of centre' to the point where the balls totally lose touch with the outer race. Although the inner race will allow this . . . even with a brand new bearing, it is possible when pressing the inner race back into line that one of the small balls could be pushed out of its bronze cage - and be very difficult to get back in place, particularly if the bearing is now mounted in the bevel housing with no access to the underside. Therefore the message is - handle with great care! It is also very important to fit the dished washer (Item No. 0007) under the lower bearing - which was designed specifically to capture any errant balls that do drop, so as to avoid them dropping into the bevel box and crunching the gears. My old mentor Titch Allen told me that this design and bearing kept Norton's Service Department in business for many years!. Finally, whenever stripping the engine down, it is always worth checking this area (and bevel box) to make sure no loose balls have made their way out. The best advice I can give is - always handle with care and never take them off centre any more than absolutely necessary!