Just adding "my two cens". I too, have had issues with something like this on a 6 and 24v system. on a 6v, they do need more (thicker) wire to draw enough power as said. but mine in one case was the started internal windings. it had a short of some kind causing ot to draw too much and hard to start. I just swapped it out, but have the old one to rebuild when I get around to it.
Cool you go it going so far though.
