Burman B52 - 28t top gear mainshaft - two types?

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sztyga20
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Burman B52 - 28t top gear mainshaft - two types?

Post by sztyga20 »

My 28t old top gear mainshaft (on right) is few mm. narrower than NOS (on left) which I've found on ebay. In every other aspect they are identical. Now I'm not sure is that NOS will be compatible with my B52 GB, or I have to make it shorter on the lathe.
Anyone knows why there are two versions of that part?
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ajscomboman
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by ajscomboman »

You'll be fine using the later deeper gear. My findings are that the earlier boxes used to jump out of top gear, this was supposedly due to the cases being machined too deeply, however I've never found any evidence of this. The recommended temp fix at the time was to fit a shim washer on the sleeve gear to allow deeper engagement with the sliding gear on the mainshaft. Later boxes had the deeper gear shown on the left and this negates the need for the washer.
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clive
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by clive »

ajscomboman wrote:You'll be fine using the later deeper gear. My findings are that the earlier boxes used to jump out of top gear, this was supposedly due to the cases being machined too deeply, however I've never found any evidence of this. The recommended temp fix at the time was to fit a shim washer on the sleeve gear to allow deeper engagement with the sliding gear on the mainshaft. Later boxes had the deeper gear shown on the left and this negates the need for the washer.
What a knowledgeable man. I heard rumour he may have just started advertising gearbox repairs. Oh no i have to tell myself off now. :rofl:
clive
if it ain't broke don't fix
raffles
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by raffles »

Carry on Clive it cuts out the middleman
Tony
Andy51
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by Andy51 »

If I remember rightly (check!) part numbers are the same across the years, which indicates parts are interchangeable. Andy
sztyga20
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by sztyga20 »

Thank you:)
Greybeard
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Re: Burman B52 - 28t top gear mainshaft - two types?

Post by Greybeard »

ajscomboman wrote:You'll be fine using the later deeper gear. My findings are that the earlier boxes used to jump out of top gear, this was supposedly due to the cases being machined too deeply, however I've never found any evidence of this. The recommended temp fix at the time was to fit a shim washer on the sleeve gear to allow deeper engagement with the sliding gear on the mainshaft. Later boxes had the deeper gear shown on the left and this negates the need for the washer.
That probably explains why I had to shim the box on my dad's 53 G9 to stop it jumping now and again in top. It may even be why the only previous owner laid a 24,000 mile bike up in his shed and left it to rust for a couple of decades. There's me thinking I'd bodged it, when all along it was an 'approved' bodge :) It's been fine for the 20 odd years since then. Pity it's 17 years too late for me to tell him why it did it :roll:
Thanks anyway. I'm rather chuffed I've learned something else this early in the day.
Steve
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