Not Charging

[fregado]

My 750L is running great, power to everything, lights, horn, plugs, etc. the omly place that I cannot get power to is the battery, it is not charging, I checked with my meter and it has no charge comming into it, any ideas where I might have lost connection? To my knowledge if the stator was bad there would be no power produced and sent to anything else. Any ideas?

[jabcb]

When starting, you need a pretty good connection to the battery to run the starter, energize the alternator field coil & power the ignition coils.

Should check voltages with and without the engine running. Voltage could be adequate to run the bike but be too low to charge the battery because of a bad voltage regulator.

I replaced the voltage regulator & rectifier with modern parts when I got my GT750. Found a crack in the old rectifier, so it was going to fail soon & give me charging problems. Got both parts for Oregon Motorcycle Parts -- both were direct replacements at a reasonable price.
http://www.oregonmotorcycleparts.com/

[tz375]

Starter, ignition, lights etc are all supplied by the battery. You could take out the alternator and run it without a battery until you ran the battery flat. As a separate issue, the alternator charges the battery. In the case of a GT the rotor is an electro-magnet I.L.O. a permanent magnet, and that complicates things a little.

Your problem could be a broken lead, a dead rotor, stator regulator or rectifier. I'd start with by checking all the connectors and leads for continuity and then test the rotor and stator for resistance (unplug them to do that). If they all check out OK, then I'd suspect the rectifier or voltage regulator. The regulator has an orange lead into it which bring is switched power. The regulator sends power to the field coils (rotor) to turn the magnet on/off. The stator has three yellow leads to the rectifier.

Follow the circuits one at a time to determine which is the problem. Those old electro-mechanical regulators can be opened up and cleaned and adjusted or replace both units with a modern solid state device from electrexworld.co.uk or Oregon.

Q. How did you determine that there's no charge to the battery? Did you check voltage across the battery as you revved the motor to watch for changes in voltage or what? That's the easiest test. As revs rise, so does voltage to a maximum of about 14v at 3000 rpm.

[fregado]

I changed the battery and it looks like it is charging now, reving the engine up a little gives a couple more volts on the meter.

[Craig380]

That's good news. If the previous battery was old, it could simply have a dud cell. Some people reckon you get only 2 - 3 years from a battery ....

[jabcb]

Good.

Should be OK if reving the engine with a fully charged battery gives you 14.2 to 14.5 volts. If it gets a lot higher than that, it could shorten the battery life. In that case you should adjust the voltage regulator per tz375 or get a modern solid state one.

I used to go thru a lot of batteries, just as Craig380 indicated. Now use a Battery Tender Junior to keep them charged up. It charges the battery & then switches to a float charge. Can leave it hooked up to a battery all winter if you want. Costs about $25 online & is a lot cheaper than buying batteries. Only need one even if you have several bikes. I have only one & several bikes to charge. I charge each battery for a day or so.

[Suzsmokeyallan]

You probably had a sulfated cell or two in that battery, these sort of conditions will suck the life out of any incoming charge.
You should consider the electronic regulator upgrade for your Buffalo as it gives a very stable charging rate for the battery, especially in the lower rpm ranges.

[fregado]

I thought I had it fixed, but apparently not. It left me stranded friday headed to work. This weekend I really got into it and after several hours messing around with it, testing the regulator, rectafier, stator, rotor, etc. by a pure fluke I discovered that one of the brushes on the rotor had a broken lead where it goes through the spring and is soldered to it's housing. A little bit of solder and she is charging like a champ.

[H2RICK]

Alright, Fregado !!!
You investigated and saved yourself a bundle of money. I love low tech solutions to high tech problems.

[fregado]

it was pure accident to find it, i pulled it to get the stator off, when i picked it up to put it back on one of the brushes stayed on the ground. i love easy cheap fixes.

[Craig380]

Good catch, you're now ready for spring & summer

[Madbuffalo]

I think out of any type of repair electrical work has to be my most dreaded just because it usually takes so much time to find the problem and then, like you said, it's usually something really simple like a broken brush wire. I remember spending countless hours replacing electrical parts on my truck trying to diagnose an electrical problem. When I finally gave in and took it to the dealer it turned out to be a faulty inertia switch. "As a test, we cut the wire to the switch and it runs great now." So one snipped wire and $200 dollars in labor later the problem was fixed. Like you said, an easy/cheap fix but very hard to find. Anyway fregado, nice work, glad you figured it out.

[uzidzit]

you have found a very very common problem with the gt750, 3 of my four have had the same issue. The nice part is a trip To ace hardware will supply the repair part. unsolder the wire left over, and buy a power tool brush just slightly big and sand down to fit the brush block, solder the wire on and presto fixed for $2.00 with stuff found anywhere. I did this just to get my gold bike to a event and it worked so well I just do this instead of buying brush blocks.