BSA unit 500 - 650 - 850 engine gear box sprocket 17 tooth product of Small Heath Birmingham plant back in the day to give great fit & supply. Long lasting materials used then to give you great performance 17t 5/8x3/8 drive chain. N.O.S product been on an old BSA dealers shelf in dry storage for years . Well greased No surface pitting forged stamping.
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