I had the standard (non "certified" 17.5 Trinity RevTech) and decided to upgrade this motor for 17.5 TC on-road racing. I purchased and installed the ceramic bearings, non metal rotor shims and the aluminum screw set for this motor (all from Trinity). At 53* timing on the motor analyzer I got about 900 rpm more w/ these three upgrades, in addition the 3 timing phases of my motor went from about 4* difference from highest to lowest down to 3* difference. I love that these ceramic bearings don't need to have any grease removed prior to installation (like other manufacturers), -it's not a big deal to remove grease but it does save time not having to do it.
Reviewed by: (Verified Buyer) erhard falk from N California.