Koyo, camshaft ball bearing. Outer, front/rear

99-06 Twin Cam (excl. 2006 Dyna) (NU)

Replaces OEM 8990/A style ball bearing. This bearing will fit will fit all models as front & rear outer cam bearings. The MoCo redesigned the Twin Cam rear outer cam bearing from ball (OEM 8990/A) to a roller bearing style (OEM 8983/MCS 921138) in 2001. This was done to help prevent failing ball bearings on, specifically, rear (=drive side) cams that are heavier loaded. This 01-up roller style bearing is a 3-piece design that is more heavy duty than a roller bearing. No other parts changed during the bearing changes. The early 99-00 style ball bearings will still fit all 99-06 models front & rear. Using front & rear ball bearings present no issues on cam driven gears.