[shadetree]

I have a very similar bike , the 2002 TRX450FM , in the fuse box is a diode , it looks like a fuse , when I got the bike it was missing from the fuse box and the P.O. have some jumper wires run to a toggle switch , I cut all that crap out , got a diode and got it back to stock , I really don't know the purpose of the diode , but I would bet you have one in there , you can test it with a OHM meter , one way would show continuity and reversing the probes it would show nothing ---------really don't know if that has anything to do with your problem , just throwing it out there

I may be but I believe a diodes purpose is to make sure power only goes in one direction? I maybe wrong. In any case I would follow what fish files has said, he sounds like he's worked on a bike or two.

you are correct on how the diodes work.