Electrical trouble with a GZ125

[theironsoldier]

I have a 2003 GZ125 (everything identical to the GZ250 besides the engine) and here is the problem I am having:

I started it up, everything working perfectly, and drove 5 miles. 8 hours later I tried to start it and nothing happened when I pressed the starter.

I checked all the switches, but no obvious problems. I checked the Starter Solenoid, and found the fuse was blown but was the wrong size (30A instead of 20A). I changed the fuse, no fix. I replaced the Solenoid itself, no fix.

I then manually connected the Solenoid contacts and it started up. Everything was working fine, including all electrical components. I drove it home, 5 miles, and found that the battery had exhausted(down to about 10v) to the point that it would not start again.

I am at a total loss as to what would cause these problems.

There are no obvious/visible faults with any of the wiring.

I can get used parts rather easily and affordably, but I am not sure what I need to replace. Any suggestions as to what would cause this?

EDIT: Above, Battery was at 10v when I returned home.

[jonathan180iq]

Take a volt meter and test across your battery terminals. You'll have 12.6 volts+/- at rest when healthy.
Do the same test with the bike running. Rev it up, and you SHOULD see 13.4-13.8 volts. (This indicates that the battery is charging)

If you see those charging numbers, it means your whole charging system is doing it's job. These are incredibly simple. You have a stator that spins when the motor is running and produces power. You have a rectifier, which simple let's current flow when it's good or it doesn't let current flow when it's bad. So if you see the charging voltage at your battery with then engine revved up, then your problem is nothing other than a bad battery.

If you DO NOT see those charging numbers on the volt meter, then we will go from there. But the battery is such a common weak point on these things that I'm banking on that.

The fact that you got the bike to start by testing the solenoid and that the starter spun and did it's job means that the starter is also totally fine. You just need to get proper juice to all of the parts or nothing will work right.

So, let's start with the battery.

HERE is some more indepth discussion on a very similar issue:
viewtopic.php?f=10&t=5954&hilit=volt+meter

[theironsoldier]

I will definitely check that as soon as the battery is recharged.

I am not sure, however, that it is the problem. The battery is nearly brand new, and at 12.6 when I was able to start the bike. It was only after I arrived back home that it would not longer start and the battery was down to about 6.5

[theironsoldier]

So here's the update with a charged battery.

Battery was at 12.1
After getting the bike started the battery was at 11.63
There was no change with revving and after about 30 seconds it dropped to 11.62

Still no response at all from the starter switch, but all other electrical works perfectly. The way I am starting it right now it by touching a screwdriver across the Solenoid leads to connect power to the Starter motor.

[alantf]

[attachment=0:31dzy3he]7.jpg[/attachment:31dzy3he]

Originally Posted by theironsoldier

The way I am starting it right now it by touching a screwdriver across the Solenoid leads to connect power to the Starter motor.

This shows that there is enough power in the battery to start the bike, so the problem must lie with the circuit that energises the coil in the solenoid. The likely culprits are the safety switches ie clutch contact, side stand relay, starter button.

[jonathan180iq]

Yep. Side stand relay is a common cure that I completely forgot about. And the starter buttons do develop some varnish over the contact surfaces over time.

That said, the fact that he didn't see an increase in volts across the leads when he revved it is a concern. Regardless of starter system circuits, he should see his battery voltage increase, right?

(Alan is the electrical guy, BTW. He'll sort you out.)

Fact is, it looks like the bike is not charging the battery, or the battery simply isn't able to hold it. Do you have anyway to load test it on the quick? In the states, any of our autoparts stores will do this service for free.

[alantf]

Originally Posted by jonathan180iq

the fact that he didn't see an increase in volts across the leads when he revved it is a concern.

I agree. Looks like there may be two problems, ie faulty safety switch, & charging problem. I didn't want to overload him at this stage, so I thought that if he got the starting problem sorted, then we could move on to the charging issue.

[theironsoldier]

Edit: see below

[theironsoldier]

Thanks for the help guys!

Unfortunately I have no easy way to do a load test... I do have a multimeter and a charger though.

Could one of the switches be the culprit for both problems? I.e. one is necessary to relay power to the battery and allow the starter switch to function?

Also, if the side stand relay is bad, wouldn't that keep the bike from starting at all just like the kill switch?

[alantf]

If you look at the drawing you'll see that the safety switches are in the low power circuit. They're designed that way, so that if a switch operates, then the bike won't start. Same if there's a fault - the bike won't start. Again, if you look at the drawing, you'll see that manually shorting out the high power terminals will let current flow to the starter motor. This is what shows that the fault MUST be on the low power side.

Your next question - The above is nothing to do with the charging circuit. That's why there appears to be two problems. If you rev the bike to 4000 to 5000 revs, and the voltage at the battery terminals doesn't rise to around 13.8v, then there's a fault on the charging circuit.

Like I said, let's go one step at a time. Get the starter problem fixed, so that's one problem out of the way, then we'll start on the charging problem.

As for the load test - Charge the battery up, then take it to anywhere that sells batteries (like garages, not stores) and they'll do the volt drop test for you. Remember, if you do have to buy a new battery, ignore the salesman, if he tells you that it's already charged. Charge it up yourself, overnight at between 0.75 and 2.00 amps. Don't use a car charger, as the output current is likely to be high.

Hope that answers your questions for the moment. Keep us posted with what you do, and the results at each step, so we can help you, and correct you if you're making any mistakes. :2tup: