Sorry, been busy as hell with some customer work.
YES, the failing battery will do it.
I thought I had here, but guess not...
The alternator on this bike doesn't "run" squat.
The BATTERY does.
The alternator makes AC power, it goes to the regulator/rectifier.
Where it's rectified (convertered) to DC power and then regulated to usuable voltage for bike... 12vdc.
The R/R gets the AC, makes it DC.... the excess DC is shunted off to ground. That makes heat. Heat kills the R/R.
This is where MOSFET R/R is great upgrade. It's digital switching.
A worthy upgrade period.
Buying a custom length harness and MOSFET R/R from Duc, supporting a long time member.
Now.... whatever R\R you're using.... the juice goes right from the battery.
Why? The WHOLE electrical system is keyed right off that bastard.
That stupid ass little battery.
Switch on..... boom...... lights on.... why? battery.
Starter....hit that switch.... boom... battery.... the relays for starting curcuit all up through the jumction box... yup ..... battery...
Bike fires.... HEY..... ignition coils get their 12vdc from.... yup... the BATTERY.
The CDI grounds the coil and it fires.... but the coils need the 12vdc from... the BATTERY.
It runs it all.
The "alternator" on this bike does nothing but make power... but it has to run through the regulator. And what does the regulator do....
Monitor the BATTERY'S voltage..... when the battery voltage drops below a certain point, the regulator kicks in. Allowing about 14 volts to the battery.
The whole bike needs 12.... the other 1-2 are there to keep the battery topped off so it has enough ass to refire the bike next time it needs to be started.
If it were an automobile, the battery wouldn't do a thing EXCEPT start the engine. Once started, the alternator powers it all.
But this ain't an automobile.
THIS is an EX500. And it's alternator doesn't do anything but feed the battery through the R/R so the battery can feed the whole bike.
Yes, it sounds complicated.... reality... nope. Pretty simple.
A simple load test with a simple multimeter could confirm a bad battery.
A simple charge test with a simple multimeter could check for bad R/R.
Depending on what you want to spend on meter.... less than $20 could've done that. For what you spent on mechanic's fees... well, you could've had a pretty nice meter.
If you want to add a bit of security... I reccommend a Gammatronix voltage light. eBay for like $20.
Wire in to battery...
Green = good overall system voltage
Yellow = below good
Red = something's crapped.
Amazing I haven't even been on in three weeks and this isn't resolved.
PUT A BATTERY IN IT!