Now I have a stator and rotor question

So I am not sure exactly which part is which. I have heard every part of the Alternator called everything.
So I will invent ways to describe what I am talking about.

So first off... when I was riding, everything would dim and the blinkers would slow down. The horn would also be noticeably affected.

So I am back to wanting to shine my shiney things and I am to the stator/generator cover and alson figured I would need to check a thing or two.

I found soot... a lot of thick soot all around the inside of the cover. Its not oil. Also, I am not sure how to tell if the brushes are worn out or not but I am guessing they are fine. There is like 1/2 inch of brush sticking out.

There was also burnt flakes loose inside the cover and the whole stator (or what I am guessing is actually the stator)... the wire part and some of the stuff that covers the wire is really flakey and very easy to come off. It is really brittle by where the wire comes out of the cover and a total.

I am like in panic mode because I have never messed with electrical before.

 

Clean it all out with some contact cleaner. Don't flake all the lacquer off the wires but don't fret it either.

The brushes have a "wear limit" line cut into them, as long as you can still see it you're fine UNLESS the little braided wires on the brushes themselves are green from corrosion.

If the bike has less than 15K on it your brushes are probably fine; the ones in my '81 550 looked brand new at 18K miles.

Order up a new gasket from chacal; they're aluminum not paper so they can be reused over and over.

If you're careful you can unscrew the brushes/brush holders from the cover and leave them hanging from the wires, and then strip and polish the cover.

The symptom you described is more indicative of a weak battery, the battery has to "support" all the systems until the charging system comes up to full output between 2500-3000rpm. If you have a weak headlight or signals that won't blink when you're idling, it's the battery for one reason or another. If it IS a charging system issue, it's not directly related other than not keeping the battery up.

Be sure to disconnect or remove the battery before you go poking about in the alternator.

 

Fitz, you are always a huge help. Thanks. i am getting some contact cleaner today.
The rotor is showing a resistance between 5.5 and 6 though. I believe it is supposed to be 4.5 but with 10% fluctuation.
The bike now only has about 15,000 on it max. My odometer was broken for a bit so I went really liberal with adding another 3,000 to the 12,450 or so that its showing.
I think my battery is actually bad though because it won't hold a full charge.
As far as the brushes go... I looked for the wear line and couldn't find it.

 

Perhaps the manual quotes a length?
Another possibility is a poor earth/ground so the greater the load, the dimmer the lights get.

Did you have any other symptoms, like will not start or turn over on the starter motor?

Clean everything up as Fitz suggests and make sure the brushes are making good contact with the rotor (Not stuck in their holders).

Once it's all back together, start the bike and see if the battery voltage increases as the revs rise. I think up to about 14 volts is ok but check your manual for the actual figure.

If the voltage stays stuck around 12 volts (and you've proved the alternator is ok), it could be wiring or the regulator. I once owned an elderly Honda CB500T and the main red wire from the regulator to the battery corroded in a connector and I got the symptoms you describe!

http://www.electrosport.com/technical-r ... iagram.pdf

Try this excellent fault finding guide, although it assumes some testing knowledge.

 

If your battery won't hold a full charge, replace it. Less than $40 at most any Auto Parts or Sears. I got one at AutoZone last season for $39.

The book does give a minimum length for alternator brushes, I'm at work and my books are at home. If you can't see the wear line then they probably are worn past it. REPLACE. They're cheap-- check with Len.

Markie is spot on in regard to connections; especially check the big plug that comes off the rectifier (the big silver heat sink with all the wires coming out) for corrosion or signs of overheating; plus all the leads to/from the battery and the starter solenoid. Also ensure the solidity of your engine ground straps.

 

I used to rebuild altenators,starters & generators and I suggest that you take the stater to a local automotive electric shop and ask them to test it. They will check the phases and insulation. If it checks good, ask them to spray it with insulation paint.

 

So the stator actually tested good despite it's appearance. i thought it was burnt out. I think I am going to replace the stator and the rotor. i have never pulled a rotor before and at the moment i am making a list for an order from chacal at xj4ever. I want to get most of what I can from him.
Anyway... the rotor is testing with too high of resistance. 4.5 I think is the standard and it is at 6 ohms. that is after going over it with 3m scoring pad and a light once over with the high grit sand paper.
The stator tests good. It looks burnt and some of the epoxy stuff on the coiul is gone. There were the flakes in the cover. But I guess if it is testing good i will still use it for now.
I have a nightmare in the wire going from the engine area to the cluster by the battery. Everything is coated with greasy, oily dirt and there is a lot of rot in the wire coatings. That could mean bare wire and not so clean connections.
I have no idea, other than the stator and brushes, where those wires go. i am completely new to electrical stuff.

 

The rotor is probably fine. Rotors typically fail by having resistance too low (shorted) or infinite (burnt or broken wire). With 10% your acceptable range is roughly 4-5 ohms. If you're reading 6 you probably are reading resistance in the meter leads or are not getting a good connection to the rotor.

The number 1 reason Yamaha charging systems fail is the plug from the stator to the wiring harness (has 3 white wires on it). Make sure it's in good condition.

Put a known good battery in it, check the voltage at 2000 RPM. If you read 14 volts you're done.

 

+1

Carl is right; there's no sense replacing things that are fine. The components you're talking about aren't all that "fragile" and as long as everything is working correctly and you get good output above 2000rpm they'll last a good long time.

You really probably only need a new battery and maybe a set of brushes.

And cleanliness.

It's amazing how many things I've "repaired" in the last 40+ years simply by carefully disassembling, CLEANING, and reassembling.

Replace the things that are meant to be replaced, like the brushes.

 

I'll add a bit to this. This connector melts as a result of higher than normal current demand placed upon the alternator. This is the result of corrosion in the wiring (usually the case) and/or loose connections. It is not the connector itself, it is merely a symptom of a larger problem. With the years our beloved bikes have seen, it has become very apparent to those of us who dare take on the electrical system that the wiring harnesses were built without regard to the future. It has been my and several other members experience that the unsealed crimp connections are the weak link in this problem. The exposed conductor (the metal strands inside the wire) has a very bad habit of wicking moisture up under the insulation and corrosion sets in. The problem with this is that current travels on the outer "skin" of the conductor strands and if this skin is covered with a layer of oxidized material, higher current levels are needed to meet the demands of the peripherals at the other end of the wire run. The charging circuit tries to make up for this additional parasitic demand but, at 19 amps, most of our bikes can only do this for a while before the wire gets hot, sometimes well beyond what the insulation is rated for. Most automotive insulation is rated up to 105C (220F) so a damaged insulator tells you that things are not right in the neighborhood. I have pulled wire runs out of harnesses and stripped off the insulation to determine how far the corrosion has progressed and found the ENTIRE run (which circuit escapes me at the moment) of wire was corroded. This means that every wire is pulling much more current than it was designed to carry, adding to the alternators woes. The cure is not cheap but can be done for under $300. Build your own harness and seal the crimp connections with either environmental sealing heat shrink (best and neatest option) or a hot glue gun and regular heat shrink. Either way, you will find that the harness will remain happy MUCH longer than the existing engineering and your charging system will thank you.
I'm sorry to be long winded on this but I see this problem more often as our bikes age. So nip it in the bud early and enjoy trouble-free operation as you ride off into the sunset.

 

Thanks you for the post.
Hi guys, Im a newbie. Nice to join this forum.
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