81 XS 650, new battery,so what the heck?

[sgtsteve]

OK, I've been on before but not for several months now. Winter and all that, ya know!

Anyhow it was time for a new battery, good one, sealed, so since it's been warm in PA I went over to storage, put the batt
in the Yamaha, choke good, bingo she starts up. Let it warm up a little and put on 15...20 miles. Runs great.

Returning to garage I notice the turn signals are barely flashing, pretty soon just an orange indicator, no flashing!
Check the horn and it got weak, very w e a k. Pull in the garage shut it down. Checked the grounds for loose
connections, all ok.

Last year this same thing happened and I found a loose ground wire, the one from the battery! OK, no now, what do you
think? Where am I? Rx to locate what's robbing me from charging? Friend local that actually rebuilt the bike two
years back and I'm always buggin' him about this stuff. Feel like a dummy and don't want to keep asking him!

thanks,
Sgt Steve BY THE WAY I LOVE THIS BIKE. MORE FUN THAT THE FAT BOY WAS AND MAYBE MORE FUN TO RIDE THAN THE SPYDER!

[madmax]

Chances are that loose ground wire caused the rotor to overheat and now it's finally died (they all go eventually and yours is 35 years old).

Check it out with a multimeter as per your haynes/Clymer manual, if the resistances are wrong then your options are getting it rewound (Custom Rewinds in Alabama come highly recommended from guys I know in SR500 forums) or consider an upgrade to a PMA which will cost more but will provide more juice much more reliably.

Max

[grizld1]

I can't agree with you on the PM alternator, Max. In most, the mount for the PMA stator doesn't fit as snugly in the supports as the OE unit, so that the only thing that keeps the stator from making contact with the rotor is a pair of 6 mm. screws from a design in which those screws were never expected to provide radial support. I've gone back to the old excited field system with a Custom Rewind rotor after a Sparx alternator failed on me in exactly that way. BTW, a Custom Rewind rotor is a significant upgrade; they use heavier wire than Yamaha did, and because of this the rotor operates at ~4 ohms rather than 5-plus. Less resistance =less heat=greater longevity.

[preston]

and SgtSteve, for what it is worth...
After checking fuses you may have,,, Please re-clean all connections put in your good condition fully charged battery back in ... when bike running let us know the voltage at the battery ( should be 13.2 or 14.3 or so ).
if battery is at same volts, running or not..... ( 12 or even 13 ),, check the brushes, clean the rotor , things like that, make sure mice did not eat a wire, while your bike was in storage.
Then, as needed, heed the advice above.
Preston

[madmax]

Mar 3, 2016 15:00:22 GMT -5 grizld1 said:

I can't agree with you on the PM alternator, Max. In most, the mount for the PMA stator doesn't fit as snugly in the supports as the OE unit, so that the only thing that keeps the stator from making contact with the rotor is a pair of 6 mm. screws from a design in which those screws were never expected to provide radial support. I've gone back to the old excited field system with a Custom Rewind rotor after a Sparx alternator failed on me in exactly that way. BTW, a Custom Rewind rotor is a significant upgrade; they use heavier wire than Yamaha did, and because of this the rotor operates at ~4 ohms rather than 5-plus. Less resistance =less heat=greater longevity.

Interesting Griz, you say the screws holding the stator to the crankcase failed? What went wrong? Vibration loosened them or did the threads pull out?

Max

[grizld1]

Max, in the OE setup the stator is held tightly on the radial axis by the supports cast into the crankcase. This arrangement prevents contact between rotor and stator and also damps vibration; if you give the screws a couple of taps with a hammer impact driver, they're not going to back out. The Sparx alternator failed when the screws loosened up and rotor and stator made contact. This happened 250 miles from home. I was lucky enough to be watching the volt meter and carrying plenty of emergency gear. After I reset the gap,retightened the screws, and brought the battery to full charge, the damaged alternator was still putting out ~13V from 1500 rpm up if I turned off the headlight, so I managed to limp the bike home. Now before you tell me that a bit of thread lock would have prevented the problem (never needed in over 20 years of experience with the OE XS650 alternator, thank you), just ask yourself how many times you've seen that much weight hung on a pair of long 6 mm. screws. In Yamaha's design the screws provide axial support only.

[sgtsteve]

Gentlemen, thank you. These XS650s are like 1957 Chevies...they should just keep making em' every year!

[sgtsteve]

Reading back over this thread I started...some thoughts came in from left field. I may not have run the bike a sufficient amount of time at a sufficient speed/rpms to allow constant charging. A friend advised me that running in traffic and not really getting any type of revs anywhere near 2500 may have been the culprit. In any case I'm putting the charged battery back in tomorrow, running the bike several miles (being aware of what I'm looking for), then checking what kind of reading I'm getting on the multimeter.

When you have nothing to do maybe a 3rd grade layout of the charging system?

SgtSteve

[preston]

And try running with "lo beam" on, ensuring High beam or some other light is not drawing your battery down ( i had a defective High beam portion of head light bulb which 40 year old generator could not keep up with)
Around lunch-time on 9th , we will be near RT 30 and Tuscarora Summit if you are near by ? (McConnellsburg PA ) send a message by 9 am, to : [e-mail] if you are near by.
Preston

[sgtsteve]

Doggone, I hadn't been on the forum in quite a while, family situation. But that area of route 30 and all...is great.
That's one of our favorite runs...out to Gettysburg and hafta' stop for lunch at the Tuscarora Summit. Also there's a great
place for ice cream in McConnellsburg about a half block off the main drag. Sorry I missed your post.

OK, fellas, here's the scoop; I'm tired of playing around. What's the thoughts on getting a stator and rotor and where would you
pick it up? I'm getting NO mag pull on the outside of the case. NONE. Even revving it up to 2,500 or so, nyet!
I've cleaned the connections but haven't done anything other than to check for magnetic pull.

Hey Griz, you comment "After I reset the gap..." on the cap? No?

Thanks in advance. I did get the bike out of storage and finally brought it over to the garage so it's safe! Trickling the battery, popped it in and started immediately but then again it always does until we run and we're not recharging.

Best Place to find a good set of directions on the rotor and stator replacement?

Sgt Steve

[sgtsteve]

Mar 8, 2016 21:08:17 GMT -5 preston said:

And try running with "lo beam" on, ensuring High beam or some other light is not drawing your battery down ( i had a defective High beam portion of head light bulb which 40 year old generator could not keep up with)
Around lunch-time on 9th , we will be near RT 30 and Tuscarora Summit if you are near by ? (McConnellsburg PA ) send a message by 9 am, to : [e-mail] if you are near by.
Preston

Max, Griz, Preston,

OK results of my latest efforts with using Curly's steps:

1) Battery charged to min of 12.7....good (actual reading 13.85)
Reading up to as high as 14.85 when revving.

3) Didn't perform.

4) Removed positive brush screw, took reading at the end of the WIRE without connection, 13.57 reading.
Reading with positive brush screw and wire connected and in place was 12.18.

5) Revved to 2500 / 3000 rpm, reading of 14.80 / 14.97 at battery.

6) First of all had to locate that wire connector...hidden partially by the left side cover. OK, checking just as step 6
directs; reading of 12.3 / 12.5 AC, repeat AC!

KEY QUESTION: WHERE IS THE DIODE/RECTIFIER HIDING?
KEY QUESTION 2: As far as I know the brushes have NEVER been replaced. Seems to me that if anything still exists and causes a problem the smart thing to do would be to get a set of brushes (the assembly) and replace regardless of anything else.

Sgt Steve

[sgtsteve]

Pre, Griz,Max,
May 2017 SUCCESS !!! My 1981 XS 650 Special runs and it charges!!!
We found the problem by an "ooopppsss". Removed the headlight bezel from the headlight due to a hex head bolt someone had stuck in the trim ring because they couldn't find a Phillips head. OK, so my buddy is checking the stator and rotor, we're checking voltage and while I'm fingering the connector from the main switch I say "hey, this connector is warm and so are the wires". Buddy says "can't be" and I tell him it is. So we read Max's hints (it is Max right?)and my buddy says let's pull the stator and brushes and get an ohm reading from the rotor. The ohm reading is less than 1.5!!!
So that explains the hot wire (literally) because it's trying to put out amps to make up for the amount of the resistance in the rotor!
Bough a rotor from a guy on ebay for $20, received it, checked the ohms...5.4!!! So we go to work and pull the old rotor, etc, etc.
Get the bike running and it's charging! THREE YEARS! Thanks to all yinz'.
Sgt Steve