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Rear Wheel Chains: Front and rear chains were originally made by Duckworth. The 1933 Spare Parts book lists “chains and sprockets”, but the 1935 Spare Parts book lists “Duckworth chains” and “Diamond chains”. It appears that at some point between 1933 and 1935, the factory began buying Diamond chains.

1929 to 1934 45” twins used a rear sprocket that had between 30 and 36 teeth. Beginning in 1935, the small twins used a larger 41 tooth rear sprocket. Rear chain #2002-29, which is 55” in length, was used from 1929 to 1934 with the smaller rear sprockets. The 1935 Spare Parts book lists both Duckworth chain #2002-15, which is 63-3/4” in length, and Diamond chain #2002-15D as being used for the 45’s from 1935 to 1957. The Diamond chain is listed as a 3/8” x 5/8”, but the length is not listed. It is presumably the same length as the Duckworth chain.

A modern "530" chain as manufactured by Diamond, D.I.D., EK, RK, Tsubaki, MSR Racing, etc. can be used as a replacement. The "5" represents the pitch (distance between pins) in 1/8" increments, in this case 5/8", and the "3" represents the width in increments of 1/8" (measured between inner plates), in this case 3/8". Modern chains are sold by length measured by the number of “links”.

Rear chain #2002-29, which is listed as 55”, has 88 links, and rear chain #2002-15, which is listed as 63-3/4”, has 102 links.

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