i have a kawasaki z650 which has a new battery fitted but each time i use the bike it slowly losses charge, i have 2 yellow wires from alternator to regulator /rectifier and a hevier duty white and red coming out of reg/rectifier which if i disconnect and put a voltmeter on and rev the bike the voltage does increase to about 14 volts that goes back through the fuse and back to the plus terminol of the battery , if i then reconnect everything and put a test across the battery it shows no sign of a voltage increase when the revs rise any ideas.

zed head, July 2009

they dont have zenor diodes in the generator, the bike has a regulator /rectifier built into one component which regulates the voltage to around 12.2 volts to 14.4 volts and also rectifies it to direct current (dc) not alternating current as it comes out of the generator like that.if you have good voltage at the yellow wires from the generator then follow the wires up to the reg/rec and check that the voltage is coming back out of it at around 12-14.4 volts it will peak at around 3000 rpm and then regulate to 12.7 at higher revs the wire coming out is usually red/white or just red also check it with the engine running and with the lights on it may be a weak generator winding(source coil) thats causing the low charging effort.i would check the resistance using an ohms meter between all the yellow charging wires in every combination(disconnected) they should all read the same resistance.

adam bike doctor, July 2009

If the voltage across the battery terminals with the engine running is around 14 volts it should be OK. Without the engine running, battery voltage should be between 12.5 and 13.0 volts (for a good charged battery). If your battery is discharged, it will take a few minutes for the battery voltage to rise, but you should see a gradual increase in battery voltage with the engine running. With the engine running, check the voltage between battery -ve and battery +ve, then between battery -Ve and your alternator +ve terminal cable, the voltage should be the same, if not, you have a break in the circuit. You should NOT run the engine with the battery disconnected as this will damage the internal Zener diodes in the alternator and the battery will discharge when at rest.

sparky, July 2009