TOPIC:

Can someone that knows what they are talking about tell me what the ac reading on the stator should read when a meter is hooked up? I aslo need to know what the dc reading is of the rectifier. My friend is having nothing but trouble with his 76 kz900......

Look at the last graphic on this page. It tells what the voltage would be for each pair of the three stator wires as measured by an AC voltmeter. The AC readings are only meaningful if the stator is disconnected from the rest of the bike.
idle is around 21vac RMS
3000 is around 45vac RMS
6000 is around 70vac RMS

www.geocities.com/loudgpz/GPZAltntrWaves...rnatorWaveforms.html

It's for a KZ 550, but it should be similar on the 900.


The rectifier output with no load, is about 70v DC or higher when the bike is revved up.

No-load tests are not necessarily a thorough test of the system, but it's a good place to start.

A better test for the stator is to hook up a 55w headlight for a car or bike to the stator wires. Be careful! It can easily blow the bulb if you rev it. It should get BRIGHT.

Same for the output of the rectifier, but with a DC voltmeter to make sure it's DC and not AC coming out of the rectifier. When the light gets bright, the DC meter should be between 10 and 20v or maybe higher.

Don't blow the bulb!

Post edited by: loudhvx, at: 2006/09/15 19:01

I have trouble following the tech stuff but my experience with a KZ900 is this...

First, check your battery by buying a small, cheap hydrometer to test the cells. You can get them at an autoparts store and it will look like an eye dropper with colored beads. If any of the cells are dead or the battery just needs to have distilled water in the cells to top them off and a charge, NONE of the electrical stuff you do later will make a bit of difference.... you have a battery problem. Don't skip this step! If the battery is OK, go on...

Take off the blue plug from the junction box. Find the three leads from the stator. They will be YELLOW wires coming off the stator. The other wires don't matter for this test. Anyway, start the bike with the plug disconnected. At idle, you should get approxiamtely 50 Volts AC when measure between any two of the three connectors on the blue plug. If you have much less, then it doesn't much matter what you do with the electrical system as the battery won't charge. The next step on the KZ900 is to figure out WHY... essentially, the problem can be the stator or rotor. You will need a service manual to tell the difference. There are impedence tests for the stator windings and if they are good, basically, the rotor will be the culprit.

If you are getting the 50 Volts AC, plug the blue connector back in. Next thing is to check the regulator or regulator/rectifier. The easiest way is to use a multimeter. Most of the time when the reg/rec goes back, the voltage will not be controlled and will tend to be way too high. Get a multimeter. Put the POS lead on the battery PLUS terminal and the NEG lead on the battery NEGATiVE terminal. Start the engine. At idle, you should get ~12.5 VDC so make sure your meter is in DC scale. Then rev the engine to 3500-4000 rpm and the reading should go up to ~14.5 VDC. If it is higher, the reg/rec is bad. On the KZ900, it is located under the battery box; well the regulator is and that is the problem. The rectifier is the two metal plates over the top of your junction box and that thing seldom goes bad. If the power is lower at 3500-4000 rpm than 14.5 VDC or so, then you MIGHT have a bad reg/rec but it is more likely the stator or rotor not doing its job.

Also check the ground and the wires. Take off the blue connector and the green connector and clean the connectors inside with contact cleaner and use a dab of dielectic grease on each connector. Bad connectors will make the charging system checks a joke and fool you into thinking you have a more expensive problem.

Thanks alot for the info, that first post made my brain hurt a lil. My friend is buying a meter right now and we are gonna do what you said step by step tomorrow, sure hope we get it running right. Once again thanks.