Battery issue...

[Devan_wick]

Hey all, I'm new to working on bikes. If anything I'm asking is stupid I apologize ahead of time.

I bought a 1980 gs850 gt off of craigslist a few weeks ago,
And it when I bought it, it would only start if it was being jumped by a car.

So I figured hey it must be the battery, so I hooked it up to my charger. Instantly the charger read full. And the guy I purchased it from said he had just bought a new battery.

I'm wondering if he may have bought a battery that's too weak?

Any tips or ideas?

[derwood]

you're doomed...

[spyug]

Welcome. It sounds like you have a dud battery. The easiest way to check is to have an autostore put it on a load tester and verify for you.

Its not uncommon so you likely will need to replace it.

so now that you are on board we need some pics of your bike and some ideas of what you intend to do with it. Also its helpful if you go into the user CP area and fill in your location and such. There may be someone local to you that you can call in for consultations if needed.

So good luck with the battery dilemma and enjoy the ride when you get it sorted.

[Steve]

Hopefully that car was NOT running when you jumped the bike.

Yes, it really matters, you do NOT want to have a donor vehicle running when connected to the bike.

.

[Devan_wick]

Alright haha well I definitely had it running....

I'll have an auto store check out the battery.

Any chance it could be faulty wiring?

[azr]

So when you jumped the bike with the car, the car was running? It could be that you have plenty of juice from the batter but at least 11 volts is not getting to the coils to fire the cylinders. Common issue with these bikes, simple fix.

[Devan_wick]

So when you jumped the bike with the car, the car was running? It could be that you have plenty of juice from the batter but at least 11 volts is not getting to the coils to fire the cylinders. Common issue with these bikes, simple fix.

Yes sir!

Ok so what's the fix then???

[Devan_wick]

Why is it that the car shouldn't be running??

[azr]

Well, first test the voltage getting to your coils. 'If' it's less than 11 volts a lot of use put a relay in. Here's the link from BikeCliff's website.

http://members.dslextreme.com/users/bikecliff/images/coil_relay_mod.html

A car battery while running has a lot more amps than a motorcycle battery. You stand the chance of wrecking your battery and your charging system. I'm not an electrical guru like others on here so I'm not sure of all the wrongs with doing it, I just know it's bad.

[eil]

Car charging systems provide too much voltage when the engine is running and can destroy the regular/rectifier. It's not a guaranteed thing, but better to err on the side of caution and never do it.

If you have a stock R/R, it's on borrowed time if it's not dead already.

What are the symptoms if when it doesn't start from the bike's battery? Doesn't turn over? Slow to turn over? Turns over fine but just doesn't start?

Test the battery at an auto parts store and don't trust anything the previous owner said. The rest, we can help you out with if you provide a clear description of the problem and the things you've already tried.

[Devan_wick]

Ok haha thanks for the knowledge!

I'll have the battery checked.

When I hooked it up to the car it would turn over super slowly...

[tkent02]

The bike regulates it's alternator by shunting the excess current to ground. It does not turn down the output like a car regulator.
It the car battery is attached, that's fine. The voltage is the same as a bike battery, but it is bigger, it can spin the bike starter forever. Again, that's fine.
But if the car engine is running, all of the current the car's alternator is making gets shunted through the bike's regulator to ground. This makes the voltage out of the car's alternator go low. The car regulator sees the voltage is low, so it tells the car's alternator to make more current. The car's alternator cam produce a lot of current, the bike's regulator cannot handle it all, it burns up.

Regardless of whether or not you have fried your charging system, a fully charged battery should spin the starter quite well. If it won't your problem is with the starter system, not the charging system. Wiring, connections, maybe the solemoid, could even be the starter itself. Make sure the ground side of the starter circuit is good as well. All of this is subject to corrosion after 30 some years.

Have you done any maintenence to this bike at all?