I have a 2000 zx12r bike was not charging put a regulator on it now it is overcharging around 15v at idle regulator getting really hot someone has run new wires from regulator to battery any ideas

You should take some measurements on your stator cables at idle. Between each pair of the three same colored cables that runs up on your regulator, you should have 14-15V at idle and 30V at 3000rpm of Alternative Current (A.C.).

Remove the seat to access the battery.
A loose battery connection will prevent charging, Tighten if loose.
If tight, start the bike.
Use a multimeter set on d/c volts or just a volt meter.
Hook red to positive and black to negative.
should read 12.50 volts - 13.50 volts at idle.
Anything under 12.50 means not charging at idle.
Rev motor to 2000 rpm. the meter should read 13.50 - 14.8. If the volts do not change, then your bike is not charging, Anything Higher than 15.0 means that your bike is overcharging, which usully fries the battery and blows the headlight fuse and/or main fuse.

If over/undercharging, this means that the voltage regulator is bad.
Before you buy another one, make sure the one you have is plugged in all the way and that the connectors are clean.
I had a GSXR 750 that sat for a while and i had to clean every connector on the bike before it would run/operate like it should, so a dirty or loose connection should be checked first.
Saves you a lot of money too because voltage regulators are usually over $100.

If you do not ride for months at a time, your battery will discharge over time.
a battery tender or battery charger is needed to keep the battery charged when the bike is not in use. Motorcycle batteries are not like car batteries, that seem to last forever. 4-5 years is about all you'll get out of a motorcycle battery on a motorcycle that is ridden alot.
On a motorcycle that is barely ridden, won't last much more than 2 years if your lucky.
Hope this information was helpful
Best regards
Big Al

Hi,,,if your battery is not charging and you have a rebuilt staor,,then your regulator/rectifier is the cause,,its job is to charge the battery.

1998 to 2002 have problem with plug to voltage regulator/rectifier which is under seat. connectors in plug overheat and bike stops charging the battery. you will see if connectors have been hot and will need to be replaced if they have.
once replaced check bike charging with multimeter at battery,should make 13.5 - to 14.5 volts just above idle. if not will need to test stator and regulator.

need to have stator checked and regulator. May have bad battery but doubt thats the only problem

14v is not overcharging. 16v is pushing it. I'm with the regulator opinion, but I would also load test your battery. If the charging system thinks your battery is low it will try to compensate by putting out max voltage, putting additional strain on the regulator, which in turn overcharges the battery... creates a vicious cycle. Is the regulator in a spot where it gets quite warm? They have a tendency to overcharge when hot. If that is the case, try relocating it or directing more airflow over it.

ah the old 5G2 nice bike.

if sat around for a year the battery will be shot, so it will not take a charge or hold it, that may be why the warning light.

after a year idle the carb jets will gunge up,

might you have no spark because the battery is so flat?

a year laid up... why.? did it have a fault then? carb diaphragms don't like being laid up, nor carb slides, one may be stuck in the old petrol residue.

think I'd be tempted to try a new battery, and if not charging, the regulator probably packed up, beware though, a shot regulator can feed ac through to the battery rather than DC, and it will bust your new battery. loads of people fall for that one.

the clutch disks are stuck together

Failed voltage regulator could do it too. If you can start the bike, put a voltmeter on the battery or charging system output. Should be around 14-15 at 3000 rpm. If it is much over that your voltage regulator is probably bad. Sometimes those regulators overcharge when they heat up too, if yours is in a location that does not get much airflow it may be possible to relocate it somewhere more "in the wind".

The reason it all goes circuslights could be that the alternator is overcharging.
The charge rate increases as the load and engine revs go up but only supposed to be a little, thats what the voltage regulator on the alternator is for.. when the regulator fails and alternator is overcharging eventually enough power is sent through the ground to light everything up and the computer cannot run properly.
High voltage levels cause sensors to read incorrectly so the computer cannot manage the engine.. Suggest you check out the charge cicuit at idle, at 2500 and at 3500 revs (briefly!)
Charge should be between 13.5 at idle, to 14.6 at 3500
Its a starting point for diagnosis.
Note that putting the alternator on a machine at Autozone will not necessarily pick up the fault - it needs to be checked ON the vehicle.
Hope this helps