So I went to my fathers this evening to rebuild the starter on his 2007 TRX500FE Foreman. Typical symptoms, hit the button and starts, next time you get the associated "click" noise from the solenoid sending power to the starter but the starter motor doesn’t turn. Verified that the solenoid was indeed sending voltage to the starter with a multimeter, time to rebuild the starter by replacing the brushes and cleaning the commutator (copper portion the brushes ride on.)

I go through the motions of removing the starter, removing the two 7mm bolts on top and pulling the bottom off, sure enough brushes are wasted and commutator is slightly burned but not pitted. Usual wear and tear on a 9 year old machine thats started almost daily. I had the brush kit already before I came to the house, so I went to rebuild it no biggie. THIS IS WHERE IT GETS INTERESTING.

I usually only remove the brush plate and pull the commutator out to put in a drill press, polish it with emery cloth in a drill press and replace it. I never take the top off the center magnet portion. Well, this time I went to redo the brushes and clean the base and handed my brother the rest of the starter to polish the base (he has the same degree I do so I trust him to not muck it up.) He took the top off the center magnet piece and disassembled it, then hands it to me in pieces to reassemble. I put the starter back together like i usually do by lining up the metal lines stamped in the top, middle, and lower housing, tighten the bolts and install the starter. I hit the button to test it, and the starter clutch whines. Hit it again, whines again like its slipping. Hit it a third time and I stop for a second.

I drove the bike up to where I was working on it, now the starter clutch is slipping? What did I do wrong? Then it hit me…THE STARTER WAS TURNING BACKWARDS. WHAT THE?!?! Following my initial confusion, I retraced my steps. Brush plates were identical, not the brushes or plates. Bike was never jumped off so voltage surge did not cause this. What could flip the polarity of the starter to turn it backwards? Wait a minute…POLARITY=MAGNETS. The magnets in the center case were installed backwards.

I removed the two 7mm bolts, pulled the bottom off, flipped the center portion of the starter over (the part that houses the magnets) and reassembled the starter lining up the marks again as usual. Reinstalled the starter, hit the button and it fired right up. I cycled the kill switch and started the bike 3 more times just to make sure I wasn’t crazy.

In the 12 years I’ve been working on bikes I’ve never done this before, and I’m dumbfounded how I stumbled upon this little factoid on accident. Needless to say I figured I would post this information here for anybody else that’s confused on their machine, and so the rest of the "regulars" can laugh at me. The more you know.