1976 KZ750 Twin Charging Issue

HI all,
I spent a good portion of yesterday reading up on KZ charging problems here in the forums and learned a great deal.

I am having a similar issue with my '76 KZ750 twin. I have installed a new battery and replaced the stator which had a burnt out field. I found that the starter had to really labor to turn over the motor. I thought it was the starter until I boosted the battery and it seemed fine then. The battery is now fully charged but still drains over time.

I then turned my attention to the rectifier. I have a Kawasaki shop manual for this bike which has been invaluable. It has a detailed section on how to test the rectifier with an ohm meter. It says to take readings from each of the 3 yellow leads to the black wire and the white wire and then to reverse the meter probes and do it again for a total of 12 readings. If the readings are either high or low in both directions, then the rectifier is defective and needs to be replaced. It also says that a normal reading should be a certain level in one direction and 10 times greater in the other direction. With my ohm meter set to 100ohm range I get a reading of about 66 in one direction on all leads and zero in the other direction. I'm not sure what to make of this.

I have also read about the headlight hi-low switch causing a similar problem. I will check this next if the rectifier turns out to be ok.

Any suggestions would be appreciated.

humourcar

humourcar wrote:

HI all,
I spent a good portion of yesterday reading up on KZ charging problems here in the forums and learned a great deal.

I am having a similar issue with my '76 KZ750 twin. I have installed a new battery and replaced the stator which had a burnt out field. I found that the starter had to really labor to turn over the motor. I thought it was the starter until I boosted the battery and it seemed fine then. The battery is now fully charged but still drains over time.

I then turned my attention to the rectifier. I have a Kawasaki shop manual for this bike which has been invaluable. It has a detailed section on how to test the rectifier with an ohm meter. It says to take readings from each of the 3 yellow leads to the black wire and the white wire and then to reverse the meter probes and do it again for a total of 12 readings. If the readings are either high or low in both directions, then the rectifier is defective and needs to be replaced. It also says that a normal reading should be a certain level in one direction and 10 times greater in the other direction. With my ohm meter set to 100ohm range I get a reading of about 66 in one direction on all leads and zero in the other direction. I'm not sure what to make of this.

Sounds bad. You should read a diode drop in one direction and INFINITE resistance the other direction ... you should not get zero on any reading. If the meter has a "diode test" range, it should read about 0.6 - 0.7 in one direction and infinite in the other direction.

If the bike pulled enough current out of the dynamo to fry one of it's windings, it's almost dead certain the rectifier assembly is hosed.