Well that didn't last long!

Found the reason for dropping 1 phase, that nasty connector between the carbs had come loose. I cleaned the connectors and greased them and all is well again.

Edit: Definitely a fault but not the big one!
 
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A little update, I removed the the stator and tested the rotor and checks out ok at 4.7ohms. I must of touched the sides of the brush holders trying to take a reading. I removed the chrysler regulator and insyalled the fiat but no change. It does charge. idle reading is 12.2v revved up reading is 13.0v. Key on only not running positive brush to ground seeing close to same numbers on battery. I did not go for ride with it. I will charge the battery again and see. I will need go thru the charging guide again to see if something has gone wrong from before I upgraded regulator rectifier. I will check it out tomorrow and report back. Better numbers will be posted tomorrow once I do all in sequence.
 
Ok so this is what I have found:
Rotor 4.7 ohms
Stator 0.4ohms on all white leads
Slap test good from previous night.
Windy nation rectifier if test is similar to the manual for continuity/discontinuity then fails. Does not have continuity from + to 1st phase but resistnace when switch meter probes. Can someone confirm this?
I do believe that I could of fried the rectifier due to over charging. On a side note, there seemed to be sand or something similar on the rectifier. Looked to be coming out of the chrysler regulator. Any ideas??
 
When measuring the rotor resistance this needs to be done at 20 Celsius or very close to. The resistance increases approximately 0.4% per degree e.g. on a hot engine at about 80 Celsius the resistance is near 6.5 Ohms, while at 0 Celsius it is about 4.8 Ohm.
 
It was 16 degrees celcius here yesterday when I measured. The engine was the same temperature as my garage as it has not been running since Tuesday evening.
 
At 20 Celsius your rotor will be about 4.9 Ohm and this lies within the Yamaha specification of +/- 10%, or in practical terms +/- 0.5V - Lucky you ;)
 
Thanks for confirming Paul. Would the windy nation rectifier test similar to the stock Yamaha with procedures from the manual?
 
I would think a rectifier test is pretty universal. It should flow or pass power in one direction but not in the other. This is a 3 phase rectifier and it appears you might only have 2 phases still working. That would give you some output but not full output. That could explain your max output of only 13 volts.
 
Well i am thinking of buying another rectifier and trying it. All else is in check. Since I have installed the Fiat regulator I can't verify if it will have a lower voltage setting to ensure it is not overcharging. Maybe the Chrysler VR38 isnt a good regulator as regulated settings are too high.
 
As pointed out by 5twins you may have one of your phases not working/connecting. It is quite rare for a stator to fail. I have had this issue as an intermittent fault for several months. The way I confirmed this was to disconnect the rectifier/regulator connector. Using an Ohmmeter set for low values place one probe on a white phase wire and touch the other probe on each of the other two white phase wires. The readings will be approximately 1 Ohm. If one phase is not connecting then this will show as an open circuit. I traced my open circuit fault back to the connector where the alternator wires connect to the harness. This is located in a difficult to get to position between the air filters on the Specials.

When my phase disconnected while riding this showed as a constant 11.6V even at 4000 rpm. Luckily this was sufficient to get me home at the time (approximately 11 miles).

Regulators have various pre-set voltages. Some used to be as high as 14.8V. The general rule is that 14.2V is the optimum voltage for charging as it minimizes overcharging and electrolysis versus charge rate. In practice the voltage range of 14.0V to 14.6V is considered acceptable. My Fiat regulator is running at 14.6 - 14.7V so is on the boarder of acceptability for long continuous running, but around town it will be OK. I only installed the Fiat regulator because I thought my other regulator was faulty but now I know it was a phase issue. Today I have reinstalled my other ACR alternator regulator which regulates nicely at 14.2V from 1800rpm upwards.

This morning I also reconnected my original stock regulator and it controls at 14.3V from 1800rpm upwards even though the book says 14.5V.

Best of luck but try to eliminate other background issues like poor electrical connections and faulty diodes before spending on new parts. Often the issue has quite a simple solution.
 
To me the original parts are robust and best. I have a completely stock day 1 charging and ignition system on my 80 special and Its above adequate. I would try used components off running bikes b4 new rewound or modern.
 
I am having a new rectifier sent to me by windy nation. So far my all my wiring is new. Worked and charged for 236kms showing 14.7 to 14.8v at running over 2000rpm. It would drop down to 13.4 or 13.5 at idle. So far rotor is at 4.7ohms, stator at 0.4 ohms on all 3 reading combinations. Regulator new Fiat as specified on another thread. Rectifier testing thru diodes have failed and on all 3 phases.
 
Superjet, let me know when you solve the problem. It may be common to both of us.

...........................Confession time, and oh how embarassing!!!!! After apparently solving my lost phase issue I went on a longish ride. I left home with the power regulating at 14.2V but after 10 minutes it dropped to 12.5V. So I continued my ride and the voltage never went higher than 13V. I bet that when the bike cools down everything will appear OK. I have tested the diodes and tested continuity to the stator and all is well.

Fxxxing intermittent faults. Must soldier on.
 
I just tested with my stock regulator and the problem persists. I conclude there is an issue down in the alternator wiring.
 
Paul what components do you have running on your bike? Are all mostly stock? It is kinda curious why it is acting similar to mine. I did check all wiring connections and all are sound. I did check resistance from both the Fiat and Chrysler regulators and got different numbers from both. Not really sure if resistance comes into effect on testing the regulator. I will only know in about 10 days before the new rectifier arrives from USA.
 
I have spent most of the day tracing the wiring and testing. I have tried 3 rectifier/regulators now with the same response. I removed my recently rewound rotor and it tests correct and powers up with a 9V battery across the copper rings - something I saw in one of Peanuts videos (Thank you Peanut). When refitted the rotor has a weak magnetic field. The brown power wire to the rotor will light a 35W bulb so no shortage of power there. I replaced the brushes because one looked poor but still nothing improved. Tomorrow I will jumper the outer ring brush directly to the regulator's green field wire just in case there is a fault in the green wire.

My SH is stock except for the Boyer ignition and I have been using the stock rectifier/regulator for my testing. I am not sure how to test an electronic regulator but eliminated this by using my other 2 regulators and getting the same results. I must revisit the slap test tomorrow also.

I tried to find a specification for the NAPA VR-38 but was unsuccessful. I did find a comment where someone said the VR-38 is a reliable regulator. It is the correct type for the later XS models and should work.

Best of Luck.
 
After a good nights sleep and 3 more hours in the garage I had made no more progress. I know the following:
  • Reg/Rec good
  • Rotor good and energized well with 9V battery placed directly on copper rings
  • Voltage at brushes = Battery Voltage
  • All connections clean and no wiring faults
  • Earthing the outer ring by wiring direct to ground gave no improvement and feeding rotor direct from battery gave weak energizing
When I first started testing I had 14 Ohms across the rotor plus the brushes. I thought that was the added resistance of the carbon brushes. But this suggested that the alternator must be very inefficient. So I removed the wires from the brushes and tested again - 14 Ohms. I removed the brushes and each measured 0.1-0.2 Ohms. Now that just doesn't add up. I assumed there must be a copper ring/brush resistance due to poor contact. So I stretched the springs a little and gave the ends of the brushes a light sand. The reassembled system still gave 14 Ohms. I then removed the brush block and lightly sanded the 2 copper rings with 400 grit. When reassembled the resistance dropped to approximately 6.4 Ohms which is about right for the rotor which was warm. I started the engine with Reg/Rec connected and the voltages were correct.

I am lead to believe that the copper rings were in some way contaminated. Of course the proof is in the riding so will do a test ride later if its fine.

Superjet, I suggest you measure the resistance (engine off) and just place the probes directly on the screw heads that hold the wires and brushes in place. It is not necessary to removed the wires so that saves some time. Perhaps your resistance is high also resulting in a poorly energised rotor????
 
Hi Paul I have just checked resistance on thr brush screws. I too have high readings (18.8 ohms) from positive lead to positive brush. Reversed gives me a slightly lower reading of 18.5ohms. I will clean up and scuff as you said to see. I did notice on the rotor of a slight wetness. Maybe in my case some of the varnish has heated and run accross the slip rings. I will report back.
 
You did put the probes across both brushes?? You want the resistance of the brush + rotor + the other brush in series i.e. hold one probe on one brush screw and the other on the other brush screw.
 
The rotor is measured directly on the rings for 5.6 ohm plus minus 10%
on cleaning rings, I used to use 600 I now clean with mineral spirits or carb cleaner on clean rags or paper toweling, then rubbing compound on a rag clean with mineral spirits. I would only use paper to round the edges of deep defects from something scraping the rotor. The brushes are very soft even compared to the copper on the rings and sandpaper leaves scratches in the copper that will wear down brushes in use. If you already sanded use rubbing compound to smooth them a bit? 2M found some great info on the complicated dynamics of the carbon brush slip ring interface.
 
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