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Top gearbox nut & bolt on Norton 850 mark 11

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Hi has anyone come across this , instead of one long bolt with a locking nut on the primary drive side ( top bolt that goes frame/ gearbox ) I've got two small treaded bolts that tread into the gearbox both sides ! I've included a photo of the bolts 

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A previous owners mod by the looks of it, possibly an attempt to overcome the gearbox moving backwards if the factory primary chain retensioning routine is not strictly followed. If the gearbox top mount has been threaded all the way through the clearance the long bolt has in the hole is now larger so allowing the gearbox to move even more. If so and you want the long bolt then sleeving of the top mount hole would restore or even improve the bolt clearance.

Thanks John for the reply I thought the same the bike has a belt drive conversion & Alton starter which was fitted by Norman white for the previous owner .

The fact the primary side bolt came loose and fell off ( luckily between the inner casing and gearbox ) seems not a great idea & it's awkward to adjust .

 I'm hoping that this might be the reason for the clutch basket drive pulley binding on the inner casing of the primary cover ? .

Kind regards Martin.

 

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I would check the cradle for any changes first, they may have opened out the holes to take the bigger diameter bolts. So a weld and redrill job or a long sleeve that extends out of the gearbox and into the cradle both sides. 

May be best to be pragmatic, if it works then tidy up with decent plated bolts and reuse. Reduced head bolts may make it easier to adjust but then not clamp up as well.

 


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