Stella - 1977D survivor, back on the road.

I bought an inexpensive VOM, but it came with really poor quality meter leads. I threw those out, and bought a much better quality pair of leads. It makes a world of difference. My meter leads always read 0.7 ohms, so I can always adjust my readings to allow for that. Its always tricky to measure low resistances.
 
Reply from Boyer Bransden:

Thank you for your enquiry, the micro power kit draws around 10 amps as a pulse when starting, this drops to around 1.0 amp when running. If you fuse the ignition unit then a 15 amp is required, if you use a smaller it will weaken after some time of running.

Regards Tech Dept.

Perfect, I had done my current figuring based on the running draw, not startup. A 5A fuse blowing is totally normal. I'll try the 15A when I get the first chance. Hopefully that will be the simple fix on ignition, which will reduce the known problems to just the rectifier.
 
And Pete, the little bit of penetrating oil fixed my steering lock. No fiddling required. I'll add a little silicone lubricant for longevity.

Thanks!
 
God stuff all around DB - someday these old gals will rumble like they were new!

Pete
 
Thanks for that bit from Boyer about the 10 Amps at startup. This explains why the voltage across the battery is so unstable when the ignition key is switched to ON. Combined with the twin tail light this means the system pulls about 14 Amps!!!! I was starting to think my new battery was dying.
 
Paul, I'm happy to report what seems to be a perfectly happy Boyer Micro Power protected by a 15A fuse. Boyer Bransden suggested I shouldn't worry about the low primary resistance on the coil. As long as she runs, it's probably just the usual difficulty of reading very low resistance as RG explains. And runs she does.

Also, my replacement rectifier came in a few days earlier than expected! Bench testing showed all good diodes and it'll get installed in the morning.

Edited for accuracy in vocabulary.
 
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DanielBlack said:
Paul, I'm happy to report what seems to be a perfectly happy Boyer Micro Power protected by a 15A fuse. Boyer Bransden suggested I shouldn't worry about the low primary impedance on the coil. As long as she runs, it's probably just the usual difficulty of reading very low impedance as RG explains. And runs she does.

Also, my replacement rectifier came in a few days earlier than expected! Bench testing showed all good diodes and it'll get installed in the morning.
Click to expand...
When talking about an ignition coil primary winding, its measured by its DC resistance only. Its wrong to use the word impedance. Impedance is the term used to measure the combination of inductance, capacitance and resistance in an AC circuit, and frequency is one of the variables. Certainly an ignition coil does have impedance, but its just not measured or used to rate an ignition coil, except possibly by design engineers.
 
retiredgentleman said:
When talking about an ignition coil primary winding, its measured by its DC resistance only. Its wrong to use the word impedance. Impedance is the term used to measure the combination of inductance, capacitance and resistance in an AC circuit, and frequency is one of the variables. Certainly an ignition coil does have impedance, but its just not measured or used to rate an ignition coil, except possibly by design engineers.
Click to expand...

Huh. I've always heard resistance and impedance as synonyms. In truth, they are closely related, but unique. And reactance is a new word for me. Thank you.
 
Wish I could be there to see that!

Hey DB - don't forget your promise to do an article on your electrical mods to Stella (incl. parts list & schematic). ;)

Pete
 
DanielBlack said:
Huh. I've always heard resistance and impedance as synonyms. In truth, they are closely related, but unique. And reactance is a new word for me. Thank you.
Click to expand...
When I was 17 I joined the Canadian Air Force, and went to trade school for a year. I qualified as a radio technician. As part of my training, we studied radio circuits which are made up of lots coils and capacitors. To know how radios work and how they can be tuned and repaired, you must have a very good knowledge of inductance, capacitance and impedance. If you work only with DC circuits, then ohms law and resistance is all you really need to know. However once you start dealing with AC circuits, such as in radios and most electronics, its a whole different ball game. Resistance can be considered alone in a DC circuit, but as soon as you start working with AC circuits, resistance is just part of impedance.
Z = √(R2 + X2)
Z= impedance in ohms
R=resistance in ohms
X= reactance in ohms
Yes, if you have never studied electronics, then words like reactance will be foreign sounding for sure.
 
You electrical guys are fantastic to follow ! Really appreciated as my "luck" surely can only go so far ... I'll be reading when my next XS is sparking ! April 9 show eh ?. . "if wishes were fishes , we'd all be swimming in riches".. -RT & rtgman , "reluctance" is my kind of word :thumbsup:
 
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This morning I started up the bike with the new rectifier plugged in. Not fully installed, just plugged in. I let her idle for fifteen minutes and all seemed well. The rectifier slowly warmed up as expected, but all seemed fine. At cold idle she had 12.5v. A few minutes in, 13v@~1200rpm. 14.2v@2000rpm and no higher up to 3000rpm.

I'm going to attribute the death of the first rectifier to inadequate heat sinking. It had been mounted to a 1/16"x~6"x~6" sheet of aluminum which clearly isn't enough to do the job.
 
I used a section of heat sink from an old computer CPU. It's been working fine now for a couple years so I guess it's adequate .....

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