Gearbox rebuild

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Gearbox rebuild

Postby Sykes » Mon Jan 07, 2019 10:04 am

Hi Guys,

Id like to get my gearbox rebuilt by someone that knows what they are at when it comes to Burmans.

Does anyone have any recommendations for a person that knows their stuff, has a quick turn around and reasonable prices?

Cheers,

E
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Re: Gearbox rebuild

Postby Rob Harknett » Mon Jan 07, 2019 10:48 am

Have you been using this bike or now building it from parts? If building from parts are you sure this is the gearbox for your bike before you start working on it. You may not be happy if you discover its not correct for your bike after getting it rebuilt. I assume the bike is approx. 1950

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Re: Gearbox rebuild

Postby Sykes » Mon Jan 07, 2019 12:02 pm

Rob Harknett wrote:Have you been using this bike or now building it from parts? If building from parts are you sure this is the gearbox for your bike before you start working on it. You may not be happy if you discover its not correct for your bike after getting it rebuilt. I assume the bike is approx. 1950



Good question Rob.

Its a Bitza im building. A 1941 G3WO frame with a 1947 AJS 350 engine and that gearbox. Im presuming it will all fit?

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Re: Gearbox rebuild

Postby SPRIDDLER » Mon Jan 07, 2019 12:47 pm

According to info in the archive the gearbox would seem to be a Burman CP type for a G3L of 1950

http://archives.jampot.dk/technical/Tra ... umbers.pdf

The CP 'box was fitted to 1947 bikes so provided that the engine plates etc. are correct it should fit your engine/frame.

For a refurb I can only suggest you contact advertisers who appear in the Jampot.
Have you looked at the 'Recommendations' section of this website?
I poke badgers with spoons.

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Re: Gearbox rebuild

Postby Andy51 » Tue Jan 08, 2019 11:20 am

These things are not difficult do rebuild yourself. The only likely bush needing replacement is the 2 bushes in the gear, driving, mainshaft. These need pressing in (easy) and boring in a 4 jaw Chuck to give approx 2 thou clearance. The rest is just dismantling, checking and reassembly - only common sense is required. As far as I know, all wearing parts are available from Jampot spares. The 'box will only go together one way (the right way!) So it is hard to make a complete dog's breakfast of the job. Bon chance! Andy

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Re: Gearbox rebuild

Postby Plugsnpoints » Tue Jan 08, 2019 6:29 pm

Andy51 wrote:These things are not difficult do rebuild yourself. The only likely bush needing replacement is the 2 bushes in the gear, driving, mainshaft. These need pressing in (easy) and boring in a 4 jaw Chuck to give approx 2 thou clearance. The rest is just dismantling, checking and reassembly - only common sense is required. As far as I know, all wearing parts are available from Jampot spares. The 'box will only go together one way (the right way!) So it is hard to make a complete dog's breakfast of the job. Bon chance! Andy



I tend to agree with this. I rebuilt my Guzzi gearbox myself years ago, replacing all the bearings, seals and return spring. The only thing I couldn't do on my own was removing a bearing race in a blind hole. Plus it had one more gear. Just take loads of photographs before during and after you take it apart. They must have had to fix them fighting Rommel in the desert!

I would definitely have a go, and it's satisfying too. :)

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Re: Gearbox rebuild

Postby Pharisee » Tue Jan 08, 2019 10:53 pm

As has already bee intimated, these old gearboxes are pretty straightforward when it comes to dismantling and reassembly. I recently stripped the seized up gearbox that came with the basket case G3/LS. Having got the outer cover off by drilling the heads off the high tensile Allen bolts it had been put together with, it looked a real mess but after cleaning everything it really wasn't that bad. All the ball races, oil seals, the few small springs and the selector drum detent plunger were replaced as was the mainshaft nut but the major components were all serviceable. It really wasn't that difficult and there was no problem with indexing the gear shift. Have a go yourself... (Ok.. this wasn't a CP box but I guess the same principals apply)

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Re: Gearbox rebuild

Postby Mick D » Wed Jan 09, 2019 8:38 am

Hi

I'm mid way through my first Burman gearbox refurbishment, a GB but essentially the same gearbox with a differing gear change cam mechanism. It all came apart easily and has been back together for a trial dry assembly with no issues.
Like Andy suggests, the sleeve gear bushes on mine need replacing and all seals, gaskets and tab washers will be replaced as a matter of course.

I'd suggest you give it a go yourself, be careful and you won't damage anything, you'll learn a lot about your bike and save yourself a fair bit of cash. :D

Andy51 - The sleeve bushes are quite thin wall, any tips for fitting other than warming the sleeve gear and freezing the bushes? I plan to use Loctite and ream to size.

Regards Mick

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Re: Gearbox rebuild

Postby oldandsmelly » Wed Jan 09, 2019 9:03 am

Hi

I've fitted many sleeve bushes to burman boxes and the best method I've found is to drop the bushes in the freezer and then press them in with a vice. They've always gone in very easy without any grief. The reaming bit sounds technical and difficult, but doesn't have to be. I use hand reamers and just take it very slowly, testing the fit every pass through. I've also found that I get better results by reaming alternatively from both directions.

Good luck!

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Re: Gearbox rebuild

Postby Mick D » Wed Jan 09, 2019 9:05 am

Hi Bruce

Are you using fixed or adjustable reamers?

Regards Mick

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