Honda OE clutch one-way bearings for 420/500/520 models. This bearing is necessary for engine braking and proper engine rpm while coasting and will wear out over time. If your machine has a lot of miles or makes a spinning noise when you shut off the engine the one-way needs replacing. The bearing is located inside the centrifugal clutch assembly and can be easily replaced while installing a primary reduction. There are two different bearings depending on if you have a footshift/ES model or a DCT(auto with ES) model. Footshift/ES models will NOT have an "A" in the model designation on the frame. For DCT's the model # must have an "A" such as 420FA or 500FPA for example.
Footshift/ES part #91101-HA0-004
DCT part # 91101-HN2-003
**Cheaper aftermarket one-ways typically don't last long or are bad right out of the box. We highly recommend going back with the Honda OE bearing.