Need to replace speedo drive in the rear wheel. The damaged existing is marked 2:1 (previously fitted with incorrect chronometric clocks) an equally damaged unit in the box of bits is marked 19:10. Yet looking through the trade ads it seems for 1969 with magnetic clocks, I might actually need a 15:12. Is this right?
Finding a good original (as…
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Speedo Drive Boxes
Attachment should be of some help.
All the UK Norton 650 Twins used a 2:1 drive box on the rear wheel. Look out for a genuine BG5330/257. Having said that I used an Indian replica version with nylon cogs in it for 6 years and never had a problem. I think the 15/12 box is for Commando or other models.
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650 Mercury
The 1968/69 Mercury's used a Smiths SSM.3001/00A for mph, and a Smiths SSM.3001/0A for Kilos. The rev-counter was a Smiths, RSM.3003/00A. The speedo cable was 5ft 5inches and the rev-counter cable was 2ft 5inches. The speedo drive was as Phil said, BG.5330/257. The rev-counter drive was BG.1508/05
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Finding a good original (as apposed to rubbish pattern) drive may be difficult ,If its any help we got our magnetic clock re-calibrated to fit with an incorrect ratio but sound old drive unit.