So this has me stumped so far... RESOLVED

[Itsnotjunk]

1990 GSX750F 43k miles.

Riding back from Philly last week and stopped to prepare for some rain I've been tracking on radar. Been having some idling issues for a couple of weeks, it stalled 5 or 6 times waiting in Philly traffic while hot, nothing new.

So I cover my packs and throw on some rain gear and hop back on the bike.

Hit the start button and solenoid clicks, and dims ALL my lights... and not a peep from the starter. I glance around the bike quick to see if anything obvious is awry but nothing has changed.

Weather is going to deteriorate fast, so I just popped started it in second and went on my way.

As the daylight faded, I noticed I had no low beam and with the high beam on I lose my taillight. Gah! Just what I need! Electrical gremlins!

So at home I have found these conditions: key on, no low beam, hit starter button and it clicks the solenoid... all the lights dim down bad and no response from starter. With the key on, I switch on the high beam which lights up, but shows massive draw (tester on good battery in this state drops down to below 6v) and I lose the taillight. Same starter condition.

If I pop start it everything seems ok except no low beam (filament looks fine) condition does not change with bulb removed.

So have the bike apart testing through the harness for grounded leads. Starting at the disconnected +battery cable, it showed continuity to ground which I thought was strange and traced it to the alternator leads, but disconnecting those leads and hooking the battery back up changed nothing with the high beam draw or missing low beam.

I'm continuing on my investigation here but does anyone have a similar experience or any suggestions what I'm looking for? A wiring diagram may be of little use, this 30 yr old bike is replete with splices, disconnected leads, etc.

Thanks in advance for any advice!

[Itsnotjunk]

Moral time...

Always, ALWAYS completely investigate the simplest possible causes of a malfuction before moving forward in diagnosing it!

It turns out all that restarting while the engine was hot, in 90°+ Philly weather evaporated the last of the electrolyte in 6 of the 8 cells in the battery. The last 2 were full, so it showed 12.6v on test and obviously the draw of the high beam with the engine off dropped it to below 6v! I was so convinced it was a bad ground I completely overlooked the battery.

I even went as far as trying to remove the lead to the starter, breaking the nearly 30yr old insulating retainer on the stud and twisting the wire of inside the starter trying to be a super mechanic! Thankfully these starters are VERY serviceable and a little epoxy resin and solder later had it good as new. 4 hours wasted on a missed fried battery. Well, now I know how easy the starter is to remove and what it looks like inside

It all started by noticing my low beam was out about 45 minutes after the starting issue. So convinced by my powers of observation that the filament was intact, it wasnt until I was completely stumped that i decided to actually bench test it, and found the low beam was burned. As soon as I realized this... "mf'er, it's the damn battery..."

[wfrpalm]

Cool that you figured it out.