Sparx ( again!)

I went for a ride over the weekend and as I rode back at dusk the bike started misfiring ( Boyer Mk3 ) and nearly ground to a halt. I turned off the headlight and it stopped missfiring but after a few miles it started again and I limped to a friend's place and left the bike there.

Now it's home I have had a look over it with a multi meter.

There is 11.5v in the battery with the ignition off.

When it's running there is 10.5v.

I have tested the stator yellow wires and they all have about 0.5 ohms between them and open circuit to ground.

There's no obvious burning /scorching on the stator, no broken wires.

I have read that a Sparx regulator won't work if the battery is low. Is that true? Could the whole issue be caused by a flat battery which won't charge up because the regulator won't work at low voltage?

Obviously my first test is to charge the battery and see if I syddenly get charging, but I thought I'd ask the experts here if there's anything else I should be checking.

Thanks

john

I don't know any reason it would need a charged battery to work. I had a Sparks regulator fail. It was a three phase and one of the diodes shorted. I reported it here and got lots of feedback that they're not too reliable although some reported no problems.

From the values you posted it seems your stator is probably OK.

JimNH said:

I don't know any reason it would need a charged battery to work. I had a Sparks regulator fail. It was a three phase and one of the diodes shorted. I reported it here and got lots of feedback that they're not too reliable although some reported no problems.

From the values you posted it seems your stator is probably OK.

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Is it possible to test the diodes? ( I do have a diode test function on my multimeter).

I had the sparx three phase regulator fail on my MK3, riding along and the red ignition/charge light came on so decided to head for home, five more miles and the bike cut out completely. Investigating at the side of the road I found the battery to be red hot. Quick as i could i removed it. Recovered the bike home and when the battery had cooled down it look as if someone had sucked the insides out, it was completely deformed!
The regulator had failed and had fed AC into the system at quite some amps heating the battery , killing the electronic ignition and the charge warning light unit. One three phase regulator from Al Osbourne, a new battery and refitted the old boyer whilst getting the Pazon repaired had me back on the road in a couple of days.
I was very lucky the battery didn't burst or explode.
Al Osbourne was very helpful on the phone (it was he who tested the sparxs reg and found its failure mode)
regards
Peter

The test you performed is part of the diagnostic(s). Before going deeper make sure that you have uniform clearance between the rotor and stator, and that there are no signs of interference between the two.

1) With a charged battery and engine off you should be able to measure 12.7 volts across the battery. The better diagnostic, regarding the battery, is to trickle charge it over night, then measure the voltage. write down the time and voltage. Measure the battery at regular intervals; when I'm at my shop I do this every 2 hours. The battery should start out at 12.7 and maintain that through out the day. If voltage drops off the battery has seen better days; if it goes below 12 volts in 8 hours it as an internal short; replace it.

2) Now start the motorcycle, and when warm enough bring the engine to 2500 RPM, you should now be able to measure 13.9 to 14.2 volts. I gather that in your case this isn't happening read on.

3) In the case where system voltage won't go above battery voltage the charging system is not well, but is it the reg/rec or is it stator/rotor? Disconnect the three yellow wires from the stator, with the engine running at or above 2500 RPM, you should be able to measure 40 to 50 VAC between any two leads, if you do, replace the reg/rec, if you don't the test you did becomes pertinent, because it points directly at the rotor losing it's gauss; many a charging system can be woken up with a new rotor.

The battery's on charge, but I'm off to work now, and by the time i get back, my neighbours won't appreciate me revving a poorly silenced Commando.
I'll do more testing tomorrow.
Thanks for the assistance.

OK I've done more testing.

With a 12.4v battery it reads 11.5v while running. Clearly there's no charging.

I tested the yellow leads from the stator while running ( having disconnected them from the regulator.
I got 27vac between each one revving to 2800 ( the rpm that it revs at on full choke).

Between yellow stator leads and ground I got 14.5v with no load.

That's a long way from the 50v suggested by Roadscholar.

The whole charging system is only a couple of years old so I'm doubting that the rotor would have lost its magnetism.

Is there any way of testing the regulator apart from replacing it?

"Test, don't guess" is my mantra. The AC voltage is low, so, follow it. Did you continuity/short check the stator?

concours said:

"Test, don't guess" is my mantra. The AC voltage is low, so, follow it. Did you continuity/short check the stator?

Click to expand...

Yes, 0.5 ohms ( aprox according to my cheap multimeter) between the yellow wires, open circuit between them and ground.

Using the diode test feature I could see that all of the diodes were working on each phase of the 3 phase except one which had a hard short (conducted both ways) to the negative DC lead. I believe you should be able to do the same test on a single phase.

Using the multimeter each AC lead should conduct one way but not the other to each DC lead. If one is open both ways or shorted both ways then the rectifier diode would be bad.

JimNH said:

Using the diode test feature I could see that all of the diodes were working on each phase of the 3 phase except one which had a hard short (conducted both ways) to the negative DC lead. I believe you should be able to do the same test on a single phase.

Using the multimeter each AC lead should conduct one way but not the other to each DC lead. If one is open both ways or shorted both ways then the rectifier diode would be bad.

Click to expand...

I've just been and checked the diodes... all good. I assume that it's possible for the regulator circuits to fail and the diodes to be OK.

Yes, I would assume that's possible. I suspect the Sparks shunts the excess DC to ground like the Zener does on the original system but don't know. Sadly I was cleaning the bench the other day and tossed the old Sparks regulator or I would have opened it out of curiosity.

pommie john said:

Yes, 0.5 ohms ( aprox according to my cheap multimeter) between the yellow wires, open circuit between them and ground.

Click to expand...

So, as mentioned by someone else, rotor magnetism is suspect, test it as well.

The below is from Dyno Dave's research - used without his explicit permission so I hope he doesn't mind

I did a few more tests with some components.
I got the phototach working and measured the max shaft speed @ 2640 rpm.
I completed the repair on the stator with silicone sleeving and E-class teflon coated 18 gauge wire to original length.
I used this stator for the following tests.

Then I remeasured the gauss of the rotors. They were tested at the keyway north pole at the edge adjacent to the next south pole and swept mid way searching for the peak strength.
They showed a range of 1530 to 1802.

Each rotor was installed and run at full rig RPM, hooked up to the 0.9 ohm load resistor. The voltage was measured with 8.65 to 10.6 AC volts indicated.

Power calculated was 82 to 127 watts @ 2640 RPM.
If you compare to the lucas chart for RM21/RM24, you can see they are poor/fair or much hotter than expected. You can look at the chart and see at about 2600 RPM the worst one which shows 9 amps or 108 watts, the best one was 127 watts.
If run to 3600 rpm you would have 10% more and at 5000rpm it should be 16% more.
So, final result...some of the rotors were not quite up to full spec and one was 141watts and the top one was 147 watts....@5000rpm.

Final comment: the bone heads that claim if the rotor magnet that sticks to a screwdriver is OK.
errrrtt WRONG
The one that is NOT up to spec DOES sticks to a screwdriver.

So perhaps the screwdriver test is just approximate and while a rotor that sticks to a screwdriver may well function, it may not function well or to full capacity.

There is a test procedure i the WSM that only requires your meter and a one ohm resistor so perhaps it would be best to do that from the start since it doesn't seem to be obvious.

If you don't have the manual Old Britts site probably has the procedure.

Take a look at these two pages where it's described how to home-grow a one ohm resistor, then apply your newly-made test tool to the stator:



Nathan

Or you can go to the local Radio Shack (good luck with that, eh?) or online and buy a 1 ohm resistor for say 50 watts, and use that.
But be careful: those babies get hot in a hurry!

I purchased one from here and am satisfied with it. http://www.surplussales.com/index/Wire-Wound-Resistors.html

It was the voltage regulator.
I bought a ( very expensive) Shindegen one from a local shop and now everything is fine. 13.5v at 2800.



Anyway, it's all good now and the shop I bought it from had the option of Lucas or Shindegen. When I asked about the difference in quality he said " I've never had a Shindegen returned as faulty."


Edited: Dyno Dave has pointed out that the figures I quoted weren't his readings.

Good news!
Which model of the Shindegen did you get?

Mr. Rick said:

Good news!
Which model of the Shindegen did you get?

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SH640D I got it from a local British bike store. I'm reluctant to tell you the price but... what the hell... $180 Australian.