Boiled Battery - Checks and Fix(es)

[FJ1100mjk]

Hi:

I'm slowly resurrecting an '85 FJ1100.

For re-painting (pretty much done, yea!) purposes, I currently have it torn down to just the motor in the frame, and the front forks and front wheel are still on it.

I bought the bike non-running without a battery in, and it looks like the missing one had cracked, boiled over, and spit all over everything on its way to the grave. This was evident by the corroded swingarm and rust-speckeled rear sub-frame, now both re-painted. And also by a two pin connector that is on a cable coming from the altenator/regulator/rectifier assembly. The two pin connector, had gotten hot, melted, and I had to shatter it with a hammer to get it apart.

I have yet to test anything, but I think from the above, it can be surmised that the regulator/rectifier, and/or alternator has gone bad.

I did a search on the forum, and have seen where folks have sourced aftermarket regulator/rectifiers, and I wanted to throw out the above to everyone for feedback on how to proceed, what to check for, what to do, and where to source parts, based upon what they found for a similar problem.

I have a brand-new Yuasa battery awaiting its installation in the near future, and I don't want to ruin it when I fire up my FJ. Nor due I want to toss out all of that sweat equity that I put into sanding and painting the parts!

Thanks in advance.
Marty

[markmartin]

Marty,

I think you're looking for specific information about regulators, but while your waiting for that, this link has some good information about installing a new battery, specifically, the initial charge.
http://bmwmotorcycletech.info/newbattery.htm

Mark

[WestOzXJR]

I have yet to test anything, but I think from the above, it can be surmised that the regulator/rectifier, and/or alternator has gone bad.

Although that is quite possible I wouldn't necessarily assume that if I were in your position, no point forking out hard-earned if you don't need to...

While your summation about about what happened to the battery may indeed be correct, there are other causes and what I'd do first off is make sure all the connections related to engine/alternator grounding are clean and in good condition and same goes for the + wires that make up the charging circuit (and starting circuit while you're at it).

What can happen is if the connections of the charging circuit are bad, the regulator doesn't reference battery voltage accurately in "deciding" how much voltage is in the battery and therefore how much to send... I see this problem all the time.

If it were me, after checking and cleaning all the relevant connections + make any necessary repairs to terminals or wiring, I'd use a remote (car?) battery to start it with a volt gauge connected across the battery and that will give you a pretty good indication of the condition of the charging circuit very soon after it starts...

You'd be looking to see no more than about 13.8 to 14 volts at about 2500 to 3000 rpm or so and a good alternator will hold that or maybe a fraction lower (13.5) with the headlight on... We started a mate's FJ11 yesterday after a re-wire and it showed 13.8 volts. Any more than this may well be within the realms of what others see on their FJ but that'll bring on premature battery failure through consistently boiling off the liquid...

And I probably should add at this point that don't forget when you're playing with batteries and jumper leads, one small spark in the vicinity of the top of battery could be KAPOWEE!!! I've seen it happen a few times before and the resultant (usually facial) burns ain't nice... So do wear some eye and face protection... It happens in a split second...

[racerman_27410]

the FJ is notorious for overcharging the battery and boiling the acid off while crusing at speed.... Randy (RPM) has a nice drop in replacement replacement rectifier that takes care of the issue completely.

while you are at it check the ground strap going to the back of the engine cases for corrosion/crunchy spots.... a bad ground will also cause havoc to the battery.

good luck on your project. 

KOokaloo!

[FJ1100mjk]

All:

Thanks for the quick replies to my post.

As part of my reassembly, I will be going over all of the electrical connectors and grounds. I had already cleaned up the main ground that's attached to the rear of the engine cases, since it was easily accessable with the carbs off.

It is prudent to first fire it up with a voltage meter inline, before I go off and buy something, just to be certain. I see in my Clymer's manual that there are a number of continuity and resistance checks for both the rectifier and the stator that I'll go over too.

If need be, I'll look into the rectifier from Randy.

Marty