Aprilia SR 125 Electrical Problems

[_sm]

Hi all.
I recently bought a 2001 Aprilia SR 125 Max Biaggi Race Rep' for getting about on during the winter.

I'll firstly state that the scooter, to the best of my knowledge, is mechanically sound and runs perfectly fine once started.
Now onto the bad news.

About 2 weeks ago I could no longer start the scooter via the electric starter button, but it would start via the kickstarter fine. I thought this may have been due to a dead/faulty battery but found it strange that the lights and horn etc still worked even when the scooter wasn't running. Up until 2 days ago everything but the electric start was working perfectly until I noticed that my turn signals were no longer flashing. Upon further investigation I found the horn was no longer sounding properly (and sometimes not at all). In regards to the turn signals, while the scooter is idleing, they flash faster than normal, but as soon as the scoot is revved they light up solid and stay solid until turned off or the scoot is brought back to idle. The lights will now no longer work unless the scoot is running.

So this morning I got myself over the garage and got my multimeter out, figuring the battery must have died. Put the multimeter on the battery only to find that it was still showing 12v or thereabouts, this is the same whether the scoot is running or not. The voltage drops when the horn, lights or turn signals are attempted to be operated while the bike isnt running but they do not function at all. The same is true when the scoot is running however the lights function properly and the indicators operate as described previously.

I am at a loss as to what may be wrong, as the battery seems to be holding and getting a charge?

Any help greatly appreciated.

sm

[finpos]

There's holding charge and there's holding enough charge to do anything useful with, and things are failing on your scoot in a direct correlation with what takes the most power. So, battery is the prime suspect.

There may be a problem with the charging circuit as well, but it's impossible to say for sure with a duff battery.

f.

[_sm]

[finpos]

The quick test is to measure the battery voltage with the engine on and the engine off, should be approx 12V (engine off) and then 14V (on, 5000rpm), however if you have a duff battery it'll trick you into thinking it's not working right, so you must always test with a known, good battery.

You seem to be getting some extra power from somewhere with the engine running, which suggests the regulator is ok.

Next step is to borrow any good battery to test with (car battery and jump leads is fine, but disconnect the suspect one), or charge the battery you have overnight, it may last a few minutes, or it may not.

f.

[hmmmnz]

i would just charge the batter for now, as that has been holding charge, but your alternator isn't charging it,

the battery had enough life to make it spark and what not, but not enough to crank over the starter,

first thing i would look at is the main fuse,
and then all the connectors between the alternator and the battery,
then find out if your alternator is ok, then look at the reg/rec
there is a wiring diagram in the wiring diagram thread
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[_sm]

I plan to take the battery to a local motorists shop in the morning, they will test the battery for free and I'll hopefully find out if the battery is duff or not.

[finpos]

Good plan, but I urge caution. The special doofer that the man in the shop will use to test your battery for free has two purposes:

1) to convince you that the battery you have is knackered and you need to buy a new one from him
2) Unless the battery is accompanied by an invoice from said man which indicates it is within warranty, in which case it's totally fine.

Also, it won't actually work properly on a flat battery, which always makes me chuckle.

However, I suspect you battery is indeed toast.

f.

[_sm]

Don't worry, I'm under no illusions as to the agenda's of most shops. The person who runs the shop is pretty genuine but either way I wouldn't be purchasing my battery from there if I happen to need a new one. This is just a quick check as they are free and local.

Just a thought, not too clued up on scooters and batterys as you may have guessed.. but could I use the battery from my zx-6 as the 'good' battery to test with?

[finpos]

yep - if it'll start your bike, it'll be fine on the scooter. Probably won't fit in the space so just use jump leads, don't forget to disconnect the flat one.

[_sm]

Update:

Borrowed a battery of a DT125 today, hooked it up to the Scoot and all fired up properly, horn, all lights and indicators work.
So this eliminates the regulator as being a suspect, correct?

That narrows it down to either a duff battery or duff alternator:

Alternator is fine, battery is duff and can't hold enough of a charge to start the Scoot.

Or.. Alternator is duff and can't put enough of a charge into the battery.

As you may have guessed I'm trying to sort this with as little cost as possible. How could I work out which is at fault without buying a new battery or alternator?

[_sm]

Thanks for the info' Colin.

So here's where I'm at currently:
I borrowed an Optimate. This Optimate has 4 lights next to 4 small icons - The 1st icon, a full battery with a , 2nd icon a half filled battery, 3rd icon a very low battery and the 4th a nearly empty battery with a . So I hooked it up to the battery and it displayed a light next to the 2nd icon which I was told is normal. Left it on for 6+ hours and came back to check. The light was now next to the 4th icon. Which I was told means the battery is as good as dead.

Readings with a multimeter are as follows:

Battery with engine off: 12.2v
While on the Optimate: 13.9v
When I attempt to start the scoot via electric start: 2v (it then jumps back up to around 11.7v then builds back up to 12.2v)
(Engine off) When I turn lights on: 0.3v (it then jumps back up to around 11.7v then builds back up to 12.2v)
(Engine off) Indicators flash fine at 11.6v

Once I get the engine running things are confusing and will result in either of the below:

(Engine on) Idle at 9.5v
(Engine revving) 6.5v
With lights on they flicker at idle but dim on revving.
Indicators flash fast at idle but stay solid when revving.
Horn is weak at idle but none existent when revving.

OR

Idles at 12-13v and rises when revved.
Horn works fine, lights work fine and brighten when revving, indicators work fine.

I also notice this change when I am out riding, my lights, indi's etc will all be working fine, then all of a sudden I notice my dash light will dim and my indi's no longer function properly and lights dim when revved.

Hope this can shed light as to what may be causing the problem.

[finpos]

Right, so, with a good battery, it works fine. With your clearly duff battery, it does all manner of mad things. I think you may be thinking about this too much. It says how to test the altenator WITH A GOOD BATTERY further up the thread, did you do that?