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Sprocket, G 21, for 520 chain

jueledwards

Forum Website User
Non-VOC Member
i have a pair of G 21 sprockets which i would like re-machined to fit 520 chains 1/4 inch wide. Should the sprockets be annealed and then machined and then re-hardened? Should they be ground down? and then what? Juel in south Carolina ,USA.
 

Robert Watson

Well Known and Active Forum Website User
VOC Member
Juel, I can turn the old sprocket off and fit a 520 "ring" (interference fit and 4 tack weld each side) for less than the cost of a new sprocket. This is dependent on the old hub and seal surface being in good shape. I'll send you a picture
 
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Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Some time ago Trevor dropped one of his bombshells on jtan, by remarking that since Vincent sprockets were 3/16" out of line, redneck obsessing about chain alignment was a waste of time. Study of the factory drawings apparently showed that they'd all been MADE like that. Having by then learned that Trevor was seldom wrong, I stored the information away, and returned to reading jtan postings about Hitler, and how, if the US hadn't foolishly interfered, he could have saved the US from communism. Or not.
Having recently had to replace the timing side gearbox bearings, and having some time earlier, on a whim, bought a laser chain-alignment tool, the removal of the G50 plate allowed me to check on Trevor's remark.
HE'S WRONG!!!!!!!
It's no more than 5/32" out of line. The outside of the rear sprocket is a mere 5/32" outboard of the outside face of the gearbox sprocket, a difference of 1/32". So if as I did, one had purchased a 520 sprocket "centred" on the 530, and planned to purchase a similar 520-centred-on 530-rear, the error would be perpetuated. And as Trevor implied, it wouldn't matter a bugger. They're all like that. But if one were an obsessive, or even if one were a perfectly sane former MPH editor, and one thought as I do about Trevor, one could see where to go next...
The good news is that Hitler apologists and communists - in this context Barack Obama - both win. If the 520 sprocket profile is "moved right" on the gearbox sprocket blank, and "moved left" on the rear sprocket blank, the centrelines are much closer together.
 

john998

Well Known and Active Forum Website User
VOC Member
Hello Tom,
I believe that the series 'D' did have a machining error on the rear chain alignment. would not be too surprised to find problems with 'B' & 'C'.
As with all things Vincent would be very reluctant to make definitive statements about it.
It would be good to be able to organise a mass chain alignment measuring throughout the club.
Regards John.
 

jueledwards

Forum Website User
Non-VOC Member
Thaks for all the replies; I have obtained from Robert Watson the needed sprocket-rings to join onto my existing old centers. which are good condition. They are beatiful work in my eye. 1/4 inch and I will take care to get them centered properly. JUEL.
 
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