Louis,
Reread and heed Sleeve's post: "12 v OR 6 v clean cable and ground strap connections go a long way in getting the starter to turn over correctly. Also with your six volt system make sure a previous owner didn't replace the cables with the later 12 volt ones, they are not of a heavy enough gauge and will cause starter problems in a six volt system."
If both your battery cables are not 1 gauge or fatter, get new cables (0 or 00 are better - also called 1/0 or 2/0).
