What stator will work?

wich setup is better in you guys opinion?

I would have to say that the permanent magnet is better cause you will have less draw on the charging sytem no haveing to excite the feild on the original 77 alt..

The 77 excited field type is actually more efficient at producing power at lower RPMs, from what I've seen. I've seen it hold 14v at idle (the same design is used on some KZ400's). The 78 and later permanent magnet design is made to make just enough power for average running. That is because the alternator is working to put out as much current as possible all the time. The regulator just burns away the excess power. If the alternator were too powerful, it would burn up reg/recs too quickly. With the 77 design, the alternator only puts out as much as needed by the bike. This type of design can be made to handle a wider range of loads over a wider range of RPMs.

The problem with the 77 design is that it is more complex and the reg/rec for it are not exactly great.

I prefer the permanent magnet design for simplicity and the option to go batteryless.

As a side note, the Kawi design for the 77 alternator is pretty sweet because it uses no brushes or slip rings as in many Honda designs. Also it requires no windings to spin as a rotor (as do Hondas). This leads to a far more reliable excited-field alternator. The Hondas and Yamis are abysmal.

Doesnt the excited feild alternator put mor of a load on the engine? I see a 100-150 rpm drop when I plug in my feild to start charging at idle. So I also did this at 2500 rpm and noticed slite drop in rpm.
So would it be safe to say that the permanent magnet gets more power to the trans with out the load on the crank that the excited feild alt puts on it.??

Snakebyte wrote:

So would it be safe to say that the permanent magnet gets more power to the trans with out the load on the crank that the excited feild alt puts on it.??

Nope, wouldn't be safe to say that at all

Takes the same amount of hp to make the same amount of electrical power regardless of which alternator type you have.

Lou stated the reason why the decrease in rpm would happen with the excited field alternator, it puts out more amperage/voltage at low rpm, and that means it consumes more engine hp at lower rpm.

With a fully charged battery the excited field alternator will consume less hp than the permanent magnet alternator, that's because the PM alternator is at full output all the time.

As a side note, the Kawi design for the 77 alternator is pretty sweet because it uses no brushes or slip rings as in many Honda designs. Also it requires no windings to spin as a rotor (as do Hondas). This leads to a far more reliable excited-field alternator. The Hondas and Yamis are abysmal.
Please note, although no boardcode and smiley buttons are shown, they are still useable

Of course you weren't including the single cam Honda 750s were you ??? No brushes and no wound rotor on any of 'em.
The only problem with the Honda setup is the electro-mechnical regulator which is not anywhere near as accurate/quick as a solid state device.
It pains me to say it but....
Another example of this same type of setup is the brand y early XS1100s which used the same type of setup.
Both of these excited field alternators are durable and will put out the juice you need within their design limits.

As Steell said, yes the excited-field type may lower RPMs more at idle since it extracts more engine shaft power to create more net electrical power at idle than a permanent magnet may. At higher RPMs, where you typically start to care about motor horsepower, the excited field alternator's regulator starts to cut back on the field current since there is so much shaft power feeding into the alternator. That type alternator only uses enough shaft power to keep the electrical system at 14~15 volts. The permanent magnet type starts to use more shaft power and creates more electrical power than the bike needs, so it gets burned away in the regulator as heat (and actually in the stator as heat as well). But at high RPMs, it's much harder to detect small changes in RPM from that load.

And H2RICK, yes I was a little too all-encompassing on my criticism of Hondas and Yams. It seems the biggest cuplrits I've come across were dual cam CB's of the early 1980's, and many small Yams like R5's, RD's, and possibly some smaller XS's. I've had to diagnose many of them (Hondas) and most needed new field rotors. The tricky part was that they superficially pass many tests. I've had rewind shops even refuse to rewind them since they seemed to test good. But the problem was fixed once they were replaced or rewound. I think engine vibration causes intermittent failure while running, but sitting, they seem fine.

Don't get me started on the RD's. My buddy's RD400 spits screws out of its field rotor about once a year. That messes up a lot of stuff under the points/alt cover.

If I'm not mistaken, the Honda 550 four single cams used a fixed field-coil alternator as well, but the few I've dealt with were very underpowered for some reason even with full voltage to the field at all times. Even with the design similar to the 77 KZ650, the Honda was still inadequate, even with the regulator out of the equation. OregonMotorcycleParts makes a good solid state reg which didn't help, and I bypassed the reg to make max power and it just came up weak, even with a new rectifier. There must just be something that fails in the stator or field, but the owner decided to just live with a battery tender instead of paying to fix it.

I'm not saying it won't happen, but I've yet to see a KZ400 or KZ650 with a bad excited-field alternator. It's usually the wiring or the reg or rec that I see go bad on the KZ's. Ok, I don't mean to sound like a commercial for KZ's, but this is a big reason why I like them.

loudhvx wrote:

Don't get me started on the RD's. My buddy's RD400 spits screws out of its field rotor about once a year. That messes up a lot of stuff under the points/alt cover.

I had three RD's at one time. All of them were 350 and all were orange but only one said YOMOMA I replaced the Yamaha letters with letters of my own.
Man those were Quick once I got the carbs set right. I had a chance to get my hands on a 400 but decided not too:( I should have bought it. I was 16 and didnt know what I had or could of had.

YOMOMA :laugh:

Yeah, those YR5's and RD's were definitely screamers that could put you on your ass if you're ham fisted.
I had to ride a stripped down YR5 a few miles without a clutch cable. I ended up doing a lot of wheelies from the stoplights... it was quite a blast!

Wahoo!! Just got these off ebay for a total of $16.41 that price includes shipping.
They are off 83 Spectre. I will be sanding the cover polishing it and slapping it on the old kz soon.

Cover pic

Damn good price!
So it's a 3-phase 750 stator, Correct?

Just curious, Dave Sloan, or OnkelB, or Ron, will the later 650/750 magnetic rotors fit on the 77 crank? If so, are all of the 650/750 stators compatible physically? Any mechanical interference? I know Kaw gives different part numbers for early and later 3-phase stators, (or was it the rotors?). Theoretically, from an electrical standpoint, I'm pretty sure a 1-phase 12-pole stator can use the same magnetic rotor as a 3-phase 18-pole stator as long as the physical fit is the same (same basic clearance etc).

Im not sure about the 77 Lou, but I know my b2 '78 model they all fit