Rick's Motorsport Electrics Starter Motor Polaris 61-509

Affordable starters are constructed with longer-life bearings than OEM many OEM starter motors have an unprotected output needle bearing on the outside of the output shafts seal; moisture can and does enter the output cap of the electric motor and follows the armature shaft to the unprotected needle bearing, which corrodes the bearing

Ricks takes the extra step of installing a double-sealed ball bearing, whith the output shaft seal on the outside of the bearing in their new aftermarket unit

This simple application of common-sense engineering does tow things: first, the outside bearing is now protected from damging water entry, and second, the sealed ball bearing is replaceable