Let me see if I understand what you have done.
wire from bat terminal on VR to left side of ammeter AND wire from L terminal of VR to left side of ammeter also ???
If this is how you have it hooked up it is not correct.
The correct hookup is: wire from BAT terminal of VR to left side of ammeter. wire from L terminal of VR feeds lights if so equipped and ignition switch if equipped with battery ignition. If you have a mag and no lights, there is NOTHING connected to the L terminal.
Only two wires to ammeter, one on each post. If the ammeter reads backward, then swap the two wires on the ammeter.