Motorcycle Repair: Starting problem, GL1100, metal shims, carbon powder

Question
Hi Mark-

Just picked up a nice condition '83 GL1100.  It will start...but...

When the start button is engaged the motor will not spin freely...it bumps to compression and won't spin.  I hooked up a portable emergency jump start battery pack and bingo, hit the button and the motor spins freely.  I replaced the aged battery with a direct match and it still bumps to compression and won't spin.  Luckily the bike starts easily and it will fire up but i'd like to fix this.

I don't understand why the jumper will work and the new battery will not.

Any advice is appreciated-

Thanks in advance-
Marshall
Phoenix, Az

Answer
Hi Marshall,

I could be way off here, but I think the starter motor is loaded with carbon powder from the brushes inside. The amperage from the new battery alone isn't enough to overcome the resistance and drag of the carbon powder inside the starter motor. The added amps of the booster put things in motion.

Starter motors can be removed, disassembled, cleaned, and reinstalled at home. Sometimes brush replacement is necessary. If you perform this task, watch and remember where thin metal shims belong. They are in the end caps and tend to separate from the end caps when disassembled. No biggie, just keep same count at each end.

Send me an email address as requested. I'll send repair information files that may assist you.

Send to: mshively1@woh.rr.com

Respectfully,
Mark Shively