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Primary Belt drive by Bob Newby

vincenttwin

Well Known and Active Forum Website User
VOC Member
Any one running an belt drive kit done by Bob Newby , if so any fitting problems, any grinding of the outer cover needed.
thanks
Peter
 

vibrac

Well Known and Active Forum Website User
VOC Member
You do not say twin or single
on a single
I have discussed this at length in the Grey Flash Diary
Bob knows the correct centers you just need to cut away about 5/8" of the inner wall surrounding the clutch in two places
follow his instructions on tension
I have never had a belt go in racing I change it every season but after the first change you have a spare
Oh and fit a crankshaft oil seal,forget chains ,oil ,vibration,clutch problems,adjustments,noise
Magic (well if you still have a Burman box -semi magic)
Twin
I fitted one to the 1275 race Egli racer had to do some mods on the length of main shaft, shaft gearbox nut and the pressure plate to get it to sit in far enough but that may have been sorted by now
Never fitted the outer cover as it was a new engine. the math went like this ((cover+standard clutch+ESA+chain+tensioner)-(bob newby kit+sheet of Alloy))=£400
at least that shows all except the clutch body sits below the joint line of the cover (see photos on www.oldracer.co.uk)
he also was playing with a double sided belt to also drive the dynamo rather than the 'sprocket from hell' not sure where that has got to (let us all know )
he is most approachable so ring him
 

vincenttwin

Well Known and Active Forum Website User
VOC Member
Thanks road going twin. Yes Bob has the two sided belt now and a nice pulley instead of the nasty plastic gear that eats it self from time to time.. getting ready next month to install and was hoping some one had already done one.
IMG_1732.jpg
 
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davidd

Well Known and Active Forum Website User
VOC Member
Bob uses a bigger clutch on the twin than the single. The single clutch will fit in the single case. I think that someone wrote on this forum that they had to space out the primary cover on the twin.

David
 

vibrac

Well Known and Active Forum Website User
VOC Member
Yes that may have been why I did a bit of work on the shaft and nut to bring the belt edge below the joint face so I could fit a flat alloy plate with a big hole for the clutch. It was not a big job mainly to clear the shaft/nut protusion inside the clutch basket against the pressure plate after modifying the shaft and nut I added about 1/8" alloy plate to the pressure plate with countersunk allen screws to get that last bit of clearance. I suppose if thats is seen as a lot of work and the belt is proud of the joint face a spacer around the cover is the other way. (thats what I had to do with my 52 Trophy to clear the clutch with a pattern chaincase) but setting the clutch that bit further back if you can just looks neater
 
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vincenttwin

Well Known and Active Forum Website User
VOC Member
Bob's clutch is a little less than 3" thick. he sells it as a replacement for the vincent clutch ,all I could get from Bob was you might need to grind a little away from the outer cover.??
 

Gerry Clarke

Well Known and Active Forum Website User
VOC Member
If it's for a road going motorcycle, is there no shock absorber anywhere in the primary drive?

Gerry
 
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Photos from the 2022 North American Rally

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