Battery going dead when bike is running..?

[thunder1295]

Charged the battery up to full and started the bike as I was tuning the carbs and the bike ran for 15 to 20 min. I turned it off when I tried
to start it again the battery was right down, need to boost it, I'm thinking the charging system isn't working.

Where should I begin finding the problem, any help would be much appreciated

Thxs
Jim

[Travis398]

Where should I begin finding the problem, any help would be much appreciated

Thxs
Jim

Start with a volt meter, see what the charging system is doing.  overcharging is pretty common. Check the fluid level in your battery too..............

[ribbert]

Charged the battery up to full and started the bike as I was tuning the carbs and the bike ran for 15 to 20 min. I turned it off when I tried
to start it again the battery was right down, need to boost it, I'm thinking the charging system isn't working.

Where should I begin finding the problem, any help would be much appreciated

Thxs
Jim

From what you describe the problem is 99.9% likely to be a hot starter motor. This is a common occurrence when the starters get a bit tired. 20 mins is not enough running to discharge the battery even it wasn't charging. 20 mins is WAY to long to leave the bike idling without some sort of cooling like a household fan sitting in front of it.

You will probably find it would start after you let it sit for 10 mins.

It is possible some gremlin is discharging your battery, like a dead short somewhere but it is highly unlikely and not worth investigating until you eliminate the well known and more likely cause.

Many, many people here have experienced bikes that won't restart immediately after turning off when hot. It is always the starter.

The fact it started with jumper cables is possibly more to do with the time it took to hook them up (cooled down a bit) than the jump start itself.

Noel

[paulfj03]

Hey jim,

I had the same problem, and it turned out to be the tired starter... After a good run, the bike would not turn over.....after charging the battery repeatedly, it would do the same thing... So, I pulled the starter cleaned it, added a rebuild kit, put it back in, and the problem was solved. The same battery is still good 2 years later. ....

Paul

[Dan Filetti]

Start simple.  Put the volt meter across the terminals with the bike running.  You should be getting ~ 13.8 volts or so.  if it's 12 or less you are not charging, if it's ~14.5 or more then you are over-charging.

If it's ~13.8, then I'd bet the starter is indeed the issue.

Dan

[thunder1295]

Thanks for all the replies, Ill start with with checking how much volts are across the terminals and move onto the starter.
Should of mention the bike sat for 4 yrs and got 36 clicks on it. There was a good wind blowing when I let it run for 20 min. well I was adjusting the carbs

Jim

[thunder1295]

I charged the battery to full, put it in the bike and got a reading of 12.6 volts. I  took out the fuse for the head light so the battery would last longer, started the bike and got a reading on the volt meter of 11.9 volts, revving the bike between 3 thou and 5 thou the volt meter would climb to 12.23 volts that was it.
The battery is brand new, so I don't think that has anything to do with it, but then again that's why I'm asking for HELP....

I cleaned off all the terminals from the generator up to the battery.

So any ideas of where I should start on repairing this would be a great help, or what you think the problem is.
Once again thanks.

Jim

[Travis398]

assuming all else is good (connections, fuses, grounds, generator plugged in) I would suspect the voltage regulator. You can take the generator off, remove the cover and test the armature, coils and rectifier with your meter. if all is good I would guess the regulator. 

[thunder1295]

I'm not sure on a few things, the generator is held on by 2 bolts I just undo them and pull off the generator that's it, sounds simple enough, watch a U tube video on changing the the regulator/rectifier so I know where that is and can check that. What about the brushes if they are worn would that cause the generator not charging enough?
Not sure where or what the armature is , is that the windings? or the coils?

Haynes manual isn't very clear on this. wish it was mechanical instead of electrical, not very good at that.

Thxs
Jim

[Travis398]

I thought there was a file on checking that here, but after looking around I guess I was wrong.

Check the brushes like you said, then check the resistance where the brushes ride (the rotor or field coil) it should be around 4 ohms.

The stator coils are connected to the rectifier on one end and connected together to ground on the other.. So you should see around .2 ohms on each of the 3 to ground.

  The rectifier can be checked where the stator wires connect to it, check 1-2 then switch the test leads and test 2-1
You will get a reading in one of them directions, but shouldn't in the other. You'll have to do this with all 3 combinations..........1-2, 2-3, 3-1

It's been a while since I have looked at one so hopefully someone will help chime in if I have misled you........

By the way 1200?  You have 3 bolts holding your generator, and yes slides right out.
Sometimes the o-ring holds it in pretty good so you may have to spin it a few degrees in each direction to free it up.

[thunder1295]

Thanks Travis, I try all that, hope I can get to it on Tues, I'll get back and post how I made out.

Thanks again
Jim

[thunder1295]

I got the alternator checked out, bad news, the shaft is giving out 17 amps so that F@#K, the regulator is toast, rectifier is good in it.
Good news got an alternator off a 87 FZ same alternator, just charging the battery and going to see if this works, picked it up at a local bike wreckers in town, otherwise its 800.00 bucks for a new one if they can get one. or make one good one out of 2.. hope this new one works.

Jim

[thunder1295]

Great news, new alternator works great....

Jim

[Tiger]

... picked it up at a local bike wreckers in town.

Zdeno's...

John.

[thunder1295]

Yes it was, Good bunch there, Al was super nice.
Think it be great to know what yrs and what other model Yamaha's have interchangeable parts.
Be great if there was a list.

Jim