Tech talk

All is never lost… there will be some­thing out there to help when things wear out and re­place­ments can’t be found… like gear change shafts for in­stance.

Classic Dirtbike - - Contents -

Reach­ing the bot­tom of Cal­lart Pass in the Pre-65 Scot­tish 2017 – it’s a good old slog up from Cal­lart Cot­tage to the view­point at the top where I’m not the only one to stop and er… take in the view shall we say be­fore at­tempt­ing the drop down to Loch Leven – I was fish­ing for the gear lever when it even­tu­ally dawned the thing was miss­ing. Luck­ily for me I was in third and able to ride along to Kin­lochleven, buy an­other lever (thanks Al­bert) and head back to fin­ish the sec­tions.

What hap­pened to the lever? I know it was tight enough on the bolt – a quick check is part of the pre-event prep. But it had still dropped off, a closer in­spec­tion post-trial showed the rea­son to be the splines the lever sits on were al­most worn off.

It’s likely to be ex­pected af­ter at least 50 years of abuse by big boots and the sce­nario goes along these lines: the lever pos­si­bly comes slack just a lit­tle, enough so it can move on the splines which wears both those on the lever and the shaft. The knock-on ef­fect is this wears the splines even more.

The old trick of clamp­ing the lever in a vice and run­ning a hack­saw through the slot will cure things for a trial or two but is lit­tle more than an emer­gency bodge. The only real an­swer is to re­place the shaft but it is all part and par­cel of the gear change quad­rant too and with BSA be­ing long gone, there’s less and less chance to find the whole thing. Luck­ily, Bur­ton Bike Bits do a re­place­ment shaft which can be fit­ted to the old one, bring­ing ev­ery­thing up to scratch again.

The idea be­hind the re­place­ment is sim­ple, mea­sure where the shaft needs to be cut and how long the re­place­ment needs to be, make sure the ends are square, line ev­ery­thing up cor­rectly and weld in place.

Such en­gi­neer­ing is beyond me but I know a lad who can and he sug­gested a slight tweak to the method. This in­volved bor­ing out the new shaft and turn­ing the old shaft down so it is an in­ter­fer­ence fit, ap­ply­ing Loc­tite en­gi­neer­ing ad­he­sive and press­ing the whole lot to­gether. Job sorted.

Though this re­pair was for BSA’S B40 model, we un­der­stand from the spec on the web­site it will work for a num­ber of other BSAS too and the feed­back on the shaft is good.

Words and pics Tim Brit­ton

Yes, em­bar­rass­ingly, at the bot­tom of Cal­lart there was no gear lever for the edi­to­rial boot to use.

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