Out of stock
SKU: MWASP520-643-50T
MPN: SP520-643-50T
The M AND W ALUMINUM PRODUCTS Rear Sprocket 50T 6.43 BC 520 Chain is a 50-tooth final-drive sprocket cut for a 6.43 bolt circle and a 520-pitch chain. It's a direct fit for builders running a 520 conversion who want a known tooth count and bolt pattern rather than guessing at a swap-meet part. At 50 teeth, it pushes gearing toward quicker acceleration off the corner, which is why it shows up on purpose-built race and sport setups. Buyers replacing a worn sprocket or finalizing a drivetrain build will find the bolt circle and pitch spelled out, so there's no measuring at the bench.
Tooth count is fixed at 50, the bolt circle is 6.43 inches, and the chain pitch is 520. Those three numbers are what determine whether a sprocket bolts up and runs true, and M AND W ALUMINUM PRODUCTS lists all three on this unit (MPN SP520-643-50T). The part weighs 0.88 lbs per manufacturer specifications, light enough to keep rotating mass down at the rear of the driveline. Match it to a 520 chain and confirm your front sprocket tooth count to land on a final ratio. If you're cutting or fitting chain during the swap, a 520 chain breaker handles the link work cleanly without prying.
Riders and racers reach for a 50-tooth rear when they want more rear-wheel torque and faster corner exits at the cost of some top speed. That trade favors tight tracks and technical courses where acceleration matters more than terminal velocity. Pair it with the right front sprocket and a fresh 520 chain to dial your final drive, and inspect it alongside the rest of your drivetrain bearings while the rear wheel is off. Browse the full drivetrain catalog for the chain, hardware, and supporting parts to finish the job in one pass.
It is cut for 520-pitch chain. Run a 520 chain and confirm your front sprocket also matches 520 pitch so the whole final drive runs the same standard.
The bolt circle is 6.43 inches. Verify that figure against your hub or carrier before ordering, since the bolt pattern is what determines a direct fit.
It has 50 teeth. A higher rear tooth count shifts gearing toward stronger acceleration and quicker corner exits, trading away some top-end speed. It suits tight, technical courses.
The sprocket weighs 0.88 lbs per manufacturer specifications. That keeps rotating mass low at the rear of the driveline, which helps responsiveness on a performance setup.
Beyond standard hand tools for the mounting hardware, you may need a chain tool if you are sizing or replacing the 520 chain during the swap. A 520 chain breaker handles link work without prying.
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