i had some problems with charging system, so i cant fix your trouble, but i can say only one, there is not so many electrics to drain accumulator.
things that i recommend you to do.
Be sure when your ACC drains, when the engine is running of when its off?
(if first - thats easy to fix, if when off - so youll get unforgetable sex )
if it drains when engine is running:
1.Take off your gas tank, then disconnect your Rectifier/Regulator connectors
2.Take a pocket tester in wire calling mode and start to check your rectifier like that:
a) connect MINUS of tester to the PLUS of rectifier and one by one check 3 phases (white wire) by the PLUS of tester.
do the same but PLUS of tester to the MINUS of rectifier and chacking one by one 3 phases
c) every time checking phases (a, you will see 0.4-0.6k resistance, if you will find one or more phases in short circuit of line brake, so know your rectifier is fucked up
P.S.: i created my own rectifier manually, so it works with 185W lightning + Music + Radio stations and Heaters.
and remember this - never believe any people that sayed you have burned your generator, you will never burn 0.8mm wire:))) i know coz i drived 1300km with 1 phase in generator was in short circuit by the rectifier and i got only 11.8V at charge:)))
and if those things will not help you, try to check wires, maybe some lamp wire or something touching ground (frame) or something like this.
and if you have guard system - firstly check this
OR!!! I got one thing, if your acc is good and rectifier is good, but touching starter button you hear "zzzzzzz". check the connections of the GROUND to the frame and theck the connections of ACC, there is 2 GROUND connections. 1st goes from generrator, and the 2nd goes from an engine
good luck ya