Rectifier caught on fire

On the 77 the five wires from the rectifier are the three yellow, and then the red/white and then the black. The green wire you speak of goes from the regulator (which is separate on the 77), so in this case you don't build it into the rectifier.

So if I were to get a permanent magnet flywheel to replace the electro magnetic one on my 77 I could snip the green wire that energizes the electromagnet.

There are only 3 wires on the stator. The green wire goes to the seperate field-coil.

The rectifier mod was originally intended for a KZ900, which happens to have a permanent magnet alternator, however it doesn't matter what type of alternator it is as long as it's 3-phase. (Single phase is almost the same, just minus one bridge-unit.)

All that matters is that the rectifier is a seperate unit (from the regulator), and does not require an auxiliary line for the regulator. (No KZ's use the aux.-out type rectifier, so it's only an issue for some other brands of motorcycles.)

If you change the alternator on a 77 650 to a permanent-magnet type, you will be removing the field coil which has the green wire on it. In my opinion, the field-coil alternator is better, especially at lower RPMs (if it's in decent shape). My friend's KZ400 hits 14v at idle (it uses the same setup as the 77 650). It's the regulator on those bikes that make the charging system seem crazy. Field-coil alternators can be made with higher output since they are regulated by the field. Permanent-magnet alternators are made to just have enough power with only a slim margin for extra lights etc. That is because the alternator is at full output at any given RPM and the regulator just dissipates the extra power as heat. If you make the alternator too powerful, the regulator burns up. This is not an issue on the field-coil alternators.

Post edited by: loudhvx, at: 2007/07/13 21:07

But I thought that the feild units took too much juice away from the battery to charge the feild?? Thats why I wanted to get a permanent magnet.

But I thought that the feild units took too much juice away from the battery to charge the feild?? Thats why I wanted to get a permanent magnet.

When the engine is turning at high RPMs, it doesn't take much "juice" to charge the field sufficiently. Remember, the power from the stator is not coming from the field, it is coming from the engine. The engine puts so much power into the equation that the field does not need to be strong. The only time you may get into a deficit is when the engine is turning slowly. However, even at idle, the KZ400 was able to get near 14v on the battery. That means there was still a net gain in electrical power.

The biggest advantages to the permanent magnet alternator are the availability of reg/rec combo units, and the simpler design. But from a performance standpoint, a good working version of the field-coil alternator is more efficient on power and should have a wider range of power delivery capability (which is why larger touring bikes often use them, as do cars). I personally prefer the permanent magnet type for it's simplicity, but I wouldn't try to change it if I didn't already have it.

One design flaw in the Kawsaki version of the field-coil charging system is the regulator-rectifier. The problem is that when the bike is not running, but the ignition switch is on, the field coil is burning a lot of power. It is important to turn the key off if the bike is not running.

Post edited by: loudhvx, at: 2007/07/15 12:32

Check out Skydailey's thread:
kzrider.com/component/option,com_joomlab...w/id,156940/catid,4/

He has a field-coil alternator. Note he's getting 15.8v at idle. Most permanent-magnet alternators won't get above 14v at idle.

Obviously, 15.8v is too high so he has some sort of wiring or regulator issue, but it goes to show the alternator is capable of putting out a lot of power.

Well right now I have a separate wire going straight to the battery that I connect and disconnect to energize the feild. I have no regulator due to the 81 550 harness on the bike. When I connect it the engine looses about 100 rpm because of the electrical load.
My whole idea is that energizing the feild takes a lot of juice away from the electrical system so the alternator is dragging the engine to put that power back into the system. Taking power away from the engine. If I were to get a magnet there will be no need for the electrical wire pulling so much juice away from the battery, hence more power the engine has.....right:unsure:

The field is not necessarily going to get full power like you are applying, that would be regulated by the regulator.

Also, the magnet using power is not what is slowing down the motor, it is the energy of the motor being converted to electrical energy by the stator that is slowing the motor. And it is creating more load than it should because you are applying full power to the field so the stator is forced to take maximun power from the crankshaft and convert it into a large power surge into the battery.

If you are running without the charging system, then the battery is low. When you connect the field to full power, the alternator takes as much power as it can from the crankshaft and surges it into the battery. That can be quite a large amount, and will probably affect the idle.

If you want to see the affects of just the magnet, then connect the field while the 3 yellow wires from the rectifier are disconnected. This will show what happens when the field is taking full power,but the alternator is not trying to surge the battery.

Also, these tests should only be done with a fully charged, good battery, otherwise poor running may arise from the low voltage condition.

Bottom line is that the field-coil alternator is more efficient since it only takes away crankshaft power as is necessary. The permanent magnet alternator puts it's full load on the crankshaft all the time. So they design the permanent magnet alternator so it's not too powerful.

Post edited by: loudhvx, at: 2007/07/16 11:23

Thank you for clearing things up for me.

Is there a way I can build my own regulator. I could find out how to do it, but I would rather just build it and not wast time on reseach do to my busy schedual:)

At the bottom of this page there is a diagram that should work for the KZ.
www.geocities.com/loudgpz/GPZvRegExciteField.html
I just Checked a local Radio Shack the other day. Unfortunately they don't carry the power transistor anymore. MCM, or Newark should have it.

I will probably update that design in order to eliminate the 50ohm, 10w R2, though, in the future. The design, in general, is over-built for the KZ, (I also used it for a truck), so I'll probably redesign it more appropriately for a KZ. Don't know when, though.

Post edited by: loudhvx, at: 2007/07/17 09:03

Thanks, hvx