82 XJ650 Cafe Build

It's been doing it since installed new brushes, my voltages increased very slightly with the new brushes in place. I purchased the brush kits from Len so it's new springs and all.

 

Have you cheked your meter against a known 12V source, like an adjustable power supply for example?

 

Hey K-Moe, yeah and I've tested with different meters as well, but I also have a voltage meter hooked up to it mounted on the top of my carbs so when I'm riding I can glance down and see what my voltage is at

 

I just did the DC amp test on the field coil wiring, got no reading with key turned on and nothing with it running either

 

I also just retested ohms across the rotor rings and the lowest reading I got was 5.9, is it safe to say I've found my problem and need a new rotor? I've already polished with fine grit paper before and didn't help I reckon.

 

Since you have some charging going on there has to be some current flowing through the field coil. I would re-check the hook-up of the wiring and the meter. Remember the positive meter lead has to be moved and the meter selection moved to dc amps.

That was discussed earlier. The higher resistance with the DMM is not necessarily indicating a fault.

As for the varying charging voltages based on which gear the bike is in that is a strange one. Speculation as K-moe suggested on brush contact and vibrations characteristics in the different gearing is the best theory yet. The only other theory is the different vibration characteristics of different gearing is causing an open / defect somewhere else in the system. That could be a stator winding opening, part of the diode bridge opening, or just a poor connection somewhere that is sensitive to that particular harmonic of vibration.

 

I noticed when I pulled the cover off that one of my brushes is already worn shorter than the other again, they're only a week old. Also my rotor rings aren't completely smooth either, they have scoring and grooves worn in them so didn't know if maybe they just aren't making good contact? Previously when I tested ohms across the rings I was at 4.8 or so but now it's higher. I also ohmed the green and brown wires and got 15.9. I've been riding it for 2 weeks now and it hasn't killed my battery so at least it's charging enough to keep the battery up!

 

The brushes will wear at different rates. That is a function of one being set at a different radius from the other; the outer brush "travels a greater distance" during each revolution than the inner brush does.

 

The only other thing I could think of is maybe pulling the rotor and cleaning the sides that contact the stator? It's pretty dirty in there, I cleaned the inner side of the stator contacts but can't reach the rotor sides.

 

There isn't anything in there to clean. The stator connections are soldered at the stator coils, so the only thing to clean is the contacts at the plug. The slip ring on the rotor is the only cleanable electrical connection on the rotor. I suppose there could be some intermittent connection due to corrosion or thermal breakdown, but that would be rare and would more likely cause infinite (or very high) resistance than it would a varying voltage condition. Still, it never hurts to look. Keep in mind that the rotor is on a taper fit and will be stubborn about being removed. You'll also need to fashion a tool to hold the rotor when you re-torque the holding bolt.

 

This is the only picture I have to describe it, I cleaned the inner "ring" of the stator and got it back to a shiny copper color, after this picture was taken. Does the "side" of the rotor not contact these? I wasn't able to reach in there to clean the grime off it. Please excuse my lack of proper terminology, I'm making it up as I go lol

 

No contact there, only an air gap. The size of the air gap affects efficiency of the system, and nothing you can do to change that. The magnetic field in the rotor generates a voltage as it moves across the stator coils, that is how voltage is generated. The stronger the magnetic field for a set speed of roation, the higher the output.

Well, I was curious about this so thought I would check it out. Note that the charging system is running open loop in this mode with the AC generator output disconnected - no voltage to the IC regulator so no feedback. That means maximum AC voltage will be outputted as the IC regulator supplies maximum current to the field coil trying to increase the output. I did not want to rev too high because of the open loop condition.

Idle of about 1100 RPM = 18.5 VAC
Rev to about 2100 RPM = 30.5 VAC

This is measuring phase to phase, and should be equal between any of the 3 wires.

 

I've got a very small oil leak from where my tach cable attaches to the motor, it's just seeping a little when the motor runs. Is this a common problem with these? It's a new tach cable. I tried an o-ring in there and also wrapped the threads with Teflon tape buts it's still doing it.

 

There is an oil seal (a real proper oil seal) that keeps the oil from going up the cable, and an o-ring that seals the tach drive to the head. Chacal has them both.

One of the best how-to articles ever written. http://xjbikes.com/forums/threads/tach-gear-housing-oil-seal-replacement-w-pics.19538/

 

Perfect! Thank you sir!

 

As soon as I read

I knew it would be a BigFitz thread. Sigh...

 

One risk inherent with rubbing an abrasive across the stationary slip rings, unless you are very careful, is to end up with a slightly unlevel contact surface. I would bet that a little too aggressive rubbing might leave low spots which might be enough to create contact voltage drop each time that spot comes around to the brush. To those who have access to a metal lathe, my best recommendation would be to recondition the scored slip rings with the rotor spinning in a lathe. You could then “face off” the copper until the scoring is gone. Most likely just a skim cut would be necessary, followed up by polishing. I’ve successfully reconditioned many a motor armature this way by turning down their badly scored commutators.
As an aside, I'd like to pass on some info I learned about brushes from literature available on several brush manufacturers websites. Brush manufacturers refer to the scoring that you see as "threading" which they claim results from insufficient spring pressure; thereby contributing to arcing between the carbon and copper. Minute particles of copper become molten during arcing process then get embedded in the brush carbon. From there you now have copper rubbing against copper which leads to galling of the slip ring face. When you replace the brushes and the slip rings are scored there is only partial electrical contact being made. More arcing is likely and more damage to both brush and slip ring.
The bushes in our bikes do not have a provision to adjust the spring pressure behind the brushes. Consequently, as the brush wears down the spring pressure decreases. I’d say that the best practice is to check your brush length occasionally and replace them as they reach their service limit as prescribed by Yamaha.

 

Is it me or is anybody else able to open his photos?

 

They were hosted elsewhere. If he pulled them then they are gone. You might try a google search. Fairly often you'll find at least the thumbnails.

 

..whats up with all missing photos?