[maddog784]

Something is telling me you don't have a good ground. If you have some extra heavy wire (8- or 6- awg) you can ground directly from the battery to the engine. If this gets it cranking normally, it would tell you that between your engine and your battery that the one of the numerous connections (engine to engine mounting plate to frame to battery box to battery) is not clean. If you can clean some of these points, you may be able to fix your problem. Di-electric grease may also be of benefit here. Also, if you've done any starter work and twisted the bolt on the back of the starter, it will go to ground and give you troubles. Take the back end of the starter off and re-align the bolt to fix that problem. Just fixed this problem over the weekend on one of mine.

Good Luck!