Burman B52 Oil Leak

Most old British bikes suffer from minor incontinence…from more than one orifice too. We usually just put up with it, apologise for the odd dribble and check our oil levels frequently.

A new oil seal just wasn’t enough

Sometimes the ‘dribble’ quickly forms a puddle and the problem needs investigating. Such has been the issue with my Burman B52 / GB gearbox on my trusty 1953 Matchless G3LS. When I rebuilt the gearbox I noticed that the gear selector shaft felt quite sloppy in its outer cover bush. I fitted a new oil seal of course and was fairly confident that would be enough. Well…it wasn’t…and after a few hundred miles I started getting frequent puddles of oil under the bike. You could see the oil was dribbling from the gear selector shaft.

One of the reasons I hadn’t fixed the problem, was that no one had a shaft in stock. I thought I’d found one at Draganfly as their system said ‘low stock – may be back ordered’…it turned out they didn’t have any and weren’t expecting any for twelve months! They did have some used ones and the helpful chap at the other end of the phone line picked out the best one they had and sent me that instead, plus a partial refund.

Part Numbers

For reference, the Draganfly Ariel part number for the gearchange spindle is ‘3718-52’ and the AMC part number is ‘G-24-2’. The outer case bush is ’20-8-9′ and the oil seal is ’27-7-4′; both are AMC part numbers and should be available from AMC Classic Spares or the AJS & Matchless Owners Club. The corresponding Draganfly Ariel part numbers are ‘3723-52’ and ‘3743-52’ respectively.

I already had the new outer cover bush which I’d bought from Steve at AMC Classic Spares.

Replacement parts were a much tighter fit

So, all the oil was drained off, the outer cover removed, and both mating surfaces cleaned up to remove the old Wellseal and gasket remnants. The outer cover was then dismantled and cleaned up, ready for heat. Heat was applied from a hot air gun to the area around the gear selector shaft bush, which was in turn, tapped out using a hammer. The cover was turned over and heated again, then the new bush was tapped in to place with a hammer. I noted that the old bush appeared to be steel, whereas the new one was brass or bronze. The used gear selector shaft was a much tighter fit in the new bush than my old one, so they were both installed, complete with another new oil seal. Note: the oil seal goes inside the gearbox and although I couldn’t find a definitive answer, I think it is installed with the flat side…with the part number on it…facing the inside of the gearbox.

Each surface received a new coating of Wellseal and a new gasket was fitted. The EP90 gear oil I had drained out was fine, so I topped it up to a pint, and once the gearbox was reassembled, filled it up and turned it over a few times…then…waited…overnight.

Success…no more incontinence

There were no dribbles in the trays so I took the bike on a trip up the road, round the block and back. The following day I noticed two tiny dots of oil in the trays, which is to be expected. Neither was from the gearbox.

The moral of this story is, when you have a gearbox, or anything else for that matter, in bits…replace anything that isn’t exactly as it should be.

I haven’t gone into detail about how to remove, disassemble and reinstall the outer cover as it’s covered in most of the Burman and AMC manuals.