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Discussion Starter #1
As I am new to the forum and sort of over whelmed by all the incredible info and sharing on this forum please bear with me in my first post as I bet this question has been asked before :)

OK so I got a 87 tw200 in very nice shape on a trade for a pw50...good deal. The guy told me the TW died and had no spark so he gave up on it.

I cleaned it up, changed oil, got it spinning nice with a booster battery pack, plug the cdi back in and hooked up my spark checker. No problem...it throw lighting bolts.

Charged up the battery on a nice long slow charge and load tested it...looks good

Fired it up today and it purrs threw the entire rpm range ( no load as it is in the shop half apart ) and checked the battery for charging.

So it is not charging , just staying at nominal voltage and loosing slowly. So because I read all this weird stuff about the 87 model year my question is:

does the 87 stator have 3 ac feed legs that feed into the regulator and is so what is a "good" AC output on this 87 tw200 ? Currently I have good Ac out on the white wire and nothing much on the other 2. is there something special with this stator that make sit different from other Yamaha bike/ quad motors?
The 4 wire regulator.. can anyone give me some info on it and how it works on this bike

So if I am asking questions that have been answered before please forgive me and send me a link.

Thanks in advance and kudos on a great TW200 site !!
 

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Discussion Starter #3
wow, yes this help tremendously, thanks.

So from what I see the white and yellow should have ac output then ?
 

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Discussion Starter #6
no prob but should be AC output on both yellow and white then.

Currently I have at idle:
white 13 vac
yellow 6 vac

on my Yamaha timberwolf quad this was way to low output and I had to replace the stator. Any input for a tw200 spec or member experiences with the 87 year ? :)
 

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I would think you should be measuring from the yellow to the white wire for AC.
The rectifier in the regulator assy will convert that to DC that you would measure to ground
from the red wire.
If you dont get anywhere, I can check it on my 87 as soon as I get the forks back together.
 

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Discussion Starter #8
I would think you should be measuring from the yellow to the white wire for AC.
The rectifier in the regulator assy will convert that to DC that you would measure to ground
from the red wire.
If you dont get anywhere, I can check it on my 87 as soon as I get the forks back together.

What does your 87 measure for ac output when measured between the yellow to white ? idle and 2000 rpm ?
 

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Now I need the clever guys on this matter. The later TW's, like the one I am rebuilding, have 4 wires instead of two ...
Instead of just the Yellow and White (as per the diagram) mine have One by Yellow and Three by White wires, all severed ....
Now on the Supplementary (01 onward) manual they show the 4 wire setup, but with all severed, which white from the alternator goes to which white on the Regulator / Rectifier unit???
Regards
Ben
 

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This is an old thread for a 1987 model with a single phase stator.

Later models have 3 phase stators with 3 white wires input to the regulator and black and red output from regulator.

Phasing does not matter, except that changing phases reverses rotation on 3 phase AC motors.

In other words, location of white wires to regulator is not an issue.

The only Yamaha schematic on this computer is for a late model XT250 which also has an AC mag with a 4th white to black/blue and red to white/red to ECU.

To check out your stator, each white to white resistance read should be the same. The manual is needed for the spec, but I would expect 0.2 to 0.4 ohm range, phase to phase.

White to ground must read infinity, or there is a short to ground.

Unregulated output with engine running on Harleys is about 20 volts per 1,000 RPM. Probably similar on a TW, but a factory service manual may provide that spec.
 
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