HD's brief foray into plastic rear sprockets.

[farmall]

Seller at Salisbury, NC swap meet had this as a conversation piece. So much for being a premium motorcycle.

[armand]

I wonder if you’d run a plastic chain to reduce wear?

[TriNortchopz]

Teeth shaped like a blade off my tablesaw.

[farmall]

I wonder if you’d run a plastic chain to reduce wear?

The theory behind those sprockets, proven on old GM V8 timing chain sprockets where HD probably got the idea, is the plastic/chain interface is not what wears, but the pin/chain interface (pin and bushing on motorcycle chains). All-steel sprockets are far more durable and the usual aftermarket upgrade since before most of us were born.

Unfortunately plastic doesn't fail gracefully, an important engineering consideration, and motorcycle drive sprockets see some nasty shock loads. I could see a quick downshift stripping that poor sprocket. Even aluminum doesn't last long hence its use on race bikes which see frequent sprocket swaps anyway.

On GM timing chains the chain usually wears until the load is not evenly distributed on the sprocket teeth then the loose chain strips them off. Chain pins/pins-and-bushings are too heavily loaded to be replaced by plastic in automotive applications at this time. Timing belts are superior shock absorbers though fitting them to interference engines is idiotic (or malice on the part of the manufacturer since they'll fail well out of warranty!).

[datadavid]

Must be an engineer who thought a plastic rear sprocket was a good idea.. if cams meet the kind of resistance and shocks a rear tire does the engine is totaled.