Burman CP Gearbox ?

Shelby-Right · Wednesday at 10:41 PM

Hi, the gearbox on my Matchless, was the only thing I didnt rebuild, it all works OK, but the sprocket seal is no good.
Now a question for all the gearbox gurus, as I've not done one. So to service the seal the mainshaft has to be removed from the box from the sleeve gear. My question is do I have to completely strip this down or can I undo the Kickstart pawls, and just slide out the mainshaft? Or will the gears not hold their position sitting on the shift forks? or do people follow that shaft out with another shaft going in?. Another Q, I was searching CP information, and I found a new old stock kick start, stop rubber, that fits on that stop peg, it's never had one and I won't pay the ebay price, but I could turn up some nylon or something, that would give a little cush?.

ando · 2026-02-20T23:32:45-0700

While it is possible to slip the mainshaft out and get it back in, if you are lucky, it is most unlikely that it can be done when you also need to replace the seal as any movement of the gearbox will move internals. Given how easy it is to strip the box I would just remove the intermediate cover, then internals. When you do so there are 12 small rollers around the selector shaft that will fall so it is best done with the gearbox standing on end. Pack them back around the shaft with grease to hold them in position on reassembly.

It is also wise to replace the bearing to sprocket spacer as it will be worn and will quickly destroy the new seal. When you reassemble the internals for the outer casing, make sure that you align the timing marks of the gear on the selector shaft and the sector quadrant assembly.

David

Shelby-Right · 2026-02-21T00:53:18-0700

ando said:
While it is possible to slip the mainshaft out and get it back in, if you are lucky, it is most unlikely that it can be done when you also need to replace the seal as any movement of the gearbox will move internals. Given how easy it is to strip the box I would just remove the intermediate cover, then internals. When you do so there are 12 small rollers around the selector shaft that will fall so it is best done with the gearbox standing on end. Pack them back around the shaft with grease to hold them in position on reassembly.

It is also wise to replace the bearing to sprocket spacer as it will be worn and will quickly destroy the new seal. When you reassemble the internals for the outer casing, make sure that you align the timing marks of the gear on the selector shaft and the sector quadrant assembly.

David

Yeah, I've already removed the intermediate cover, I wanted to check third gear, the gear box had been done up, but 3rd gear bush was new but had. 0055" clearance, so I've made a new bush and it's got about. 0015" now. I had already bought the special sprocket bearing, so I've fitted that, and machined up a seal adapter the internal seal steel ring was like new, when I pulled it apart the sprocket nut wasn't tight, but had two lock tabs bent over, that will get 70ft lbs tomorrow.
Cheers.

Burman CP Gearbox ?

Shelby-Right

ando

Shelby-Right

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