Motorcycle Repair: 1968 Honda CL 350 Starter, honda cl 350, head gasket

Question
The bike has been sitting un-started for over 2 years.  I did a head gasket and related but never bench tested the starter,  After reassembly the starter acted as if the battery was dead or dying but it is brand new.  
I removed it from the engine, took off the brush cap to find a bunch of wet soot like material.  Once cleaned and reassembled (backwards) it bench tested fine.  I then realized the cap was on backwards and reversed it, bench tested again but it was stuck, like a clutch was engaged.  I repeated the reversal twice more getting the same results, good when assembled backwards, N/G when correct.  What could be the problem?

Answer
Daniel, One brush is "hot" and the other one is grounded to complete the circuit. It should spin over in either configuration because there is no changes internally. You do have to have all the parts in alignment and not allow the through bolts to short out against the field coils. There are tiny detents that index the covers and plates inside the starter motor. It doesn't take much to get them out of alignment and cause problems.

If you are not able to sort it out on your own, check with a local shop that rebuilds alternators and starter motors. Make sure that the brush lengths are sufficient to contact the armature for the future.

Hard to say much more about it, without seeing the parts in person.

Bill Silver