If you are just wanting to know if the rectifier is chucking out enough to charge the battery, just start the scoot and put the leads on the batt and if it's chucking out 14.5 volts it's ok, if not it could be a loose wire or corrosion as I experienced.

If you look at hughie's test procedure on my earlier post, it sounds a bit more complicated than that to investigate: http://www.maxi-muppets.co.uk/forum/vie ... 10&t=10354

But certainly that's the first thing i'll try. I'll check the voltage on idle as well as on hightened revs and see what readings i get. I don't want to be disassembling fairings on a cold sunday morning unnecessarily if i can deduce from just a simple check.

Ok just done a quick check on the battery after fully charging it. When i unplugged the charger, the voltage was showing something like 11.70v, fired up the engine and it shot up to 12.60v

Revved the bollocks off it but couldn't get it to go over 12.80 no matter what i did.

Idle with nothing on shows a dropping on the voltage. seen it go down all the way to 11.60 before i revved and it shot up to 12.50ish.


If i turn on the lights and rev to a normal level, such as when riding, i see the voltage sustained at around 12.50.

if i turn on the grip heaters (full on) it takes a sharp turn downwards and revving the engine only manages to slow it down.

So is this a rectifier issue then?

To me that sounds like a coil has gone down.
I think your next steps are something like this.
Remove the left side panel that sits under the seat.
Look for the white connector that contains 3 white wires, (there may be more in it) unplug it.
Start the bike
Set the voltmeter to AC
Check the voltage between any two white wires with the engine running at 3000rpm or higher
Now do the same with another two white wires
Now do the same with the last two white wires
You are looking for at least 50 volts AC on each reading sometimes up to 70 – 75 volts AC
The kicker is that they should all be about the same.
If one is low then the whole bike is running on two coils and with a lot of tests on the battery the voltage will look fine but a bit at the low end but there will be little amps to back it up. So the battery will slowly go flat.

Second test is with the connector still unplugged and the meter set to ohms, connect one test lead to earth / chassis or even the –ve of the battery will do. With the other test lead touch all of the white wires one at a time and the reading should be open circuit or infinity, if you find that one is not then you have a coil breaking down and shorting to earth.

Stator is now needed; a remanufactured one is about £100 and is not difficult to fit.

Hope this helps

P.S. 12.60v is not enough, it should read 13.80v with the engine running at 3000rpm or even 14.1v is the battery is in a low er state.
From memory if a diode has gone in the reg/rect the voltage drops to about 11v to 11.5v when reving the tits of it and about 9.5v on idle

hope this helps

Another p.s. if you get a reading of 14.5v across the battery with engine running at any speed you may have a duff meter or the reg/rect is passing too much voltage and may cook your battery

Thanks Deeping. I'll have to do these checks next weekend as I'm not feeling well today and the bloody freezing weather's just making things worse. From what you said though it sounds more like a stator issue. I'll try riding without the heated grips this week and only use headlight when it's dark.

I think your battery is faulty. It should read 12.7 volts fully charged.
Anything lower indicates poor cranking power.
It is charging, but cannot reach 14.4 volts, because the battery is one cell short.

I bought the battery back in february, i doubt it's battery being duff...

Hi Halfabusa, sorry I've been out of it since Saturday. Hope you are feeling a bit better, I too have been unwell. Ate something that disagreed with me. Still not great. I agree with Dave, your battery is almost certainly f**cked. It must read at least 12.6v+ after charging at rest and preferably just a tad more. With your bike running at idle it should read in the region of 13.5v and when revved to 3000 must be making at least 14+ volts but never more than around 14.9v - 15v. If above that the rectifier is not doing it's job and is 'overcooking' the battery. That may be what has happened of course. Deeping is giving good testing advice so do that if you can and come back with your results. Good luck!