RGS Rear sprocket

[Sunbeam]

Could anyone help me identify the rear sprocket off my 1962 RGS. It's 1/4 × 5/8 chain size. I've looked on the internet and the only one I've seen similar with the large holes through the drum casting is at Surrey cycles who sell it as G/Star, RGS Alfin Racing rear sprocket....but this is 3/8 × 5/8. I know BSA changed to 3/8 × 5/8 chain 1957- 62...could BSA have fitted the 1/4 × 5/8 size to RGS models during this period?....thanks...Howard.

[Sakura]

I've never seen a 1/4 x 5/5" chain on any 650 BSA, nor yet an Alfin sprocket. More likely Goldie. Rocket Goldies differed in many ways to Super Rockets but that's not one difference I have ever noticed. However, 60 odd years have passed so who knows? John Gleed perhaps, if he's still around. I first bought mine in 1968 and that only had the usual sprocket/brake drum then.

[Sunbeam]

Many thanks Sakura, i appreciate your information.

Regards.

Howard.

[Swarfcut]

 Roy Bacon's Twin Restoration lists final drive as 0.625 x  0.0400 x  0.380",  99 pitches for 1962/1963. Page 215/1986 Edition.

 Narrower chains were fitted to lower powered ranges, sprocket fittings and dimensions are the same, so an element of mis-match and swaps is possible.

 If this sprocket came off a running bike, the gearbox sprocket will be wrong for the model as well, again narrower teeth to fit the chain.

 Gold Star used 5/8 x 1/4 until  1958, then moving to 5/8 x 3/8. Roy Bacon again, "Gold Star and other Singles".  1985/p146.

 So  it could actually be an early Gold Star transmission, but not strictly correct for a more powerful machine.

 Swarfy.

[Rex]

Bacon's books are an interesting read but not to be trusted as absolutely and totally correct.

[Sunbeam]

Thanks to all who answered my post. Its seems to add up with everything I've had to put right. The gearbox sprocket was 1/4 × 5/8...so the rear sprocket must have been off an earlier gold star. ...regards....Howard.

[berger]

or the sprocket was off a raced bike for lighter weight i have one turned down for a 1/4 chain .

[Sakura]

Thanks to all who answered my post. Its seems to add up with everything I've had to put right. The gearbox sprocket was 1/4 × 5/8...so the rear sprocket must have been off an earlier gold star. ...regards....Howard.

If the teeth are good why not use it, unless you're building a concours garage queen? It's part of the bike's history.  You'll be unusual if you wear it out!