rectifier

Hello all,

I recently had problems with a battery discharging too fast.
I checked the battery voltage at 1500 rpm and it read 15.5 V, at 4000 rpm it was still 15.5V. So it was stable but rather on the high side I think (newbie to this all). Is this normal?

Later I measured my rectifier and found out that one diode gave the same resistance in both directions. So I suppose a new rectifier is necessary.

What I was wondering is the following: in case the 15.5 V that I measured is too high, could this be caused by the fact that my rectifier was broken?

Take care,

Jan

I'm a real dolt when it comes to electrics so I'll let one of the electrical gurus here answer your overcharging question. If you are going to buy a new rectifier though I can reccomend someone. Check this guy's site oregonmotorcycleparts.com/rectifiers3p.html

I had a rectifier wire fry on my 77 650 C-1 this spring and I bought one of his. It works great, costs less than OEM and is guaranteed for life.

It seems that 30 years is the lifespan for the factory part, several guys here have had the same problem and this guy told me he has sold a bunch of these this year, more than he has since he started making them.

Just thinking out loud that the rectifier diode failure may just be a symptom and not the actual fault.

If your '77 KZ650-B1 is one of the early ones like mine, your battery charging voltage is actually controlled by an old-time mechanical regulator located under your left cover. This regulator is not complex but expensive to replace ($100 plus I understand). Here is what I learned about mine and I think it may be apply to you at this time.

There are three wires attached. The wires are:

- Black/Yellow - Ground wire. This wire goes to Battery Negative (-).

- Brown - Voltage Sensing wire. This wire comes from the Ignition Switch. When the Ignition Switch is ON, it is connected to the White wire from the 20 Amp Main fuse which is feed by the White/Red wire to a “Y” junction hidden in the harness. At this “Y” junction it connects to the Red wire leading directly to the Battery Positive (+) and it also connects to another White/Red wire going to the Positive (+) input of your Rectifier. At the Rectifier you will notice that a Black wire connects to the Rectifier Negative (-).

- Green - Alternator Field Winding Control wire. This wire goes to the Alternator’s output voltage control winding. This is the wire that controls the charging voltage level. If this control signal is wrong or if it is intermittent then the charging voltage can never be right. In fact, if this control signal does not even reach the Alternator then the charging voltage will always be maximum which will first boil your battery electrolyte away and then start blowing your light bulbs. I am unsure if it will affect your Rectifier diodes but they should at least run hotter.

1) Check the lugs and if they are not real clean then clean or replace them. Do this at both ends of the wire. Crimping the new lugs is good but soldering them is better (in my humble opinion).

2) Check the wires and if they are brittle and or cracked and or discoloured by over heating replace them.

3) Open up the regulator and look at the condition of the relay contacts inside. If they are really bad try filing lightly with a very fine file... it worked for me. Check the wire leads to each of the sensing resistors inside and if one is broken fix it. Finally, get a manual and find the “1977 Model” regulator adjustment procedure. Follow the procedure and diagrams carefully and you will be surprised at the good results you can get.

If you are unable to get the Regulator within specifications then you may need to replace it and replace the Rectifier.

Here is one of the diagrams I drew to explain it to myself.



Hope this helps. Best of success.

Post edited by: bill_wilcox100, at: 2007/09/23 10:50

As Bill mentioned, the rectifier wouldn't cause the voltage to be too high. But if the tests show a bad reading, it may be on its way out. You may want to replace it.

Either the regulator is out of adjustment or the wiring to the regulator is losing voltage.

Gringo's link is for the rectifier, and is a great deal at $45. Or you could try to make one for $20 if you like to tinker:
www.geocities.com/loudgpz/GPZdiy3phaseRectifier.html

This page has the 650 regulator you may need. A great deal at $50:
www.oregonmotorcycleparts.com/vregulators.html
After 30 years, the mechanical regulator will have pits and burns on the contacts. Even if it's not the problem, the solid-state regulator will give better regulation.

The brown wire on the regulator powers the regulator. If the voltage on the brown wire is low, the regulator will incorrectly increase the power to the alternator in order to compensate. This ends up with the battery voltage getting too high.

The voltage on the brown wire takes a long path to get to the regulator. The most likely places for voltage loss is in the main fuse and/or ignition switch.

To test this, compare the voltage on the brown wire connection on the regulator (while bike is running, and everything is connected normally) with the battery voltage. It should be about the same. If the battery is higher by more than 1/2 a volt, then you'll need to check the fuse box or the ignition switch for bad connections.

Also, the black ground wire on the regulator should have zero volts on it. That can also cause the problem.

Post edited by: loudhvx, at: 2007/09/24 11:01