Balanced components of an electrical system

[J Vreede]

There’s a description of my project bike, in the introductory post I made 26Jul, that I have questions about. The bike came to me basically finished but for the electrics. It was running when I first bid on it (on the NZ equivalent of Craigslist), but it was withdrawn from auction because its Pamco ignition had blown up. I figured it was just the original ‘74 voltage reg/rec and/or the cobbled up wiring mating the later engine to the earlier wiring loom, so I bought it not running and started collecting the materials, like a MOSFET reg/rec and wiring stuff from Revival Cycles, to do a complete rewire, as I want it to be as reliable as possible.

I didn’t recognize it in 2016, but it’s pretty apparent looking back through the archives, that 200W permanent magnet alternators, big coils and Pamco ignition on a std ‘74 XS regulator/rectifier were mismatched. The seller bought another Pamco w/advancer to go with the bike, probably amongst the last Pete sold, as by the time I got around to looking at how to install it, he’d stopped selling them. Other events then overtook any further work on the XS, until now.

My question is what actually was mismatched about these components and why? Can someone who lived through that period pls tell the story?

Things that come to mind from reading past posts:

• PamcoPete’s musings that Pamco failures seemed to be associated with the PMA’s and big coils – was that inherent in this combination or was it a Pamco failing?
• Are 2 big coils something that the Pamco ignition just can’t cope with or are all the alternate electronic ignitions similarly affected?
• Is there some reason (other than space) that coils with dual leads (wasted spark) seem to be preferred or recommended by the ign. mnfr’s?
• The bike doesn’t need a 200W alternator to run and its obviously going to dump some (most?) of it as heat, so it needs a good reg/rec, but my Ducati Monster has a 520W alternator, doesn’t have a Mosfet reg/rec and doesn’t blow up its electrical components. Is there anything inherently bad about PMA’s on XS650’s?
• Seems that a number of the last Pamco units were defective. Even though I have a new (untried) one, should I be looking for an alternative for reliability’s sake?
• Given the bike has a 200W PMA that I can't replace, what other electrical components would you choose now, so that they’re balanced and reliable?

Please excuse all these questions, but it seems likely that the story of what happened, would likely wrap them all together anyway
Thanks - jv.

 

[Signal]

I will have a lash at answering.

• PamcoPete’s musings that Pamco failures seemed to be associated with the PMA’s and big coils – was that inherent in this combination or was it a Pamco failing?

Sorry no idea. What coils do you have?

• Are 2 big coils something that the Pamco ignition just can’t cope with or are all the alternate electronic ignitions similarly affected?

Most ignitions are designed to work with coils with a primary resistance within a certain range eg 3 to 5 Ohm for TCI systems and around 0.5 Ohm for CDI systems. Stick to the manufactures recommendations and you are fine.

• Is there some reason (other than space) that coils with dual leads (wasted spark) seem to be preferred or recommended by the ign. mnfr’s?

I think it boils down to cost and ease of manufacture. 1 pickup, 1 coil, 2 bumps on the trigger wheel 180 degrees apart. There are some drawbacks with a wasted spark ignition and single coils are used in preference by at least one ignition expert I have spoken to recently when performance is the overriding objective. Heaven knows why Yamaha opted for dual points and coils on the XS, but it was their first 4 stroke.

• Is there anything inherently bad about PMA’s on XS650’s?

No not in my opinion but you need to have good components ie not Chinese knock offs. I have an XS running a RD 350 pma and RD 250 Reg/rec bought from local wreckers and it works reliably. So much so on a multi day ride my XS was used to charge a battery from a Z 650 that had its charging system die on the trip. I prefer to buy used components from a wrecker if I can.

• Seems that a number of the last Pamco units were defective. Even though I have a new (untried) one, should I be looking for an alternative for reliability’s sake?

I think only you can answer that question, can you afford another ignition, how much will you be riding the bike. How hard do you find wiring bikes. If you want a new ignition there are a few cam triggered options out there.

Given the bike has a 200W PMA that I can't replace, what other electrical components would you choose now, so that they’re balanced and reliable?

Well if your Mosfet reg/rec is the real McCoy fit that and you will be good from all accounts. Only other thing I like to fit is a catch diode to the starter solenoid but that’s just me. There is a thread (maybe on this site?) I have seen that tells you how to spot a knock off Mosfet reg/rec.

 

[gggGary]

I've got 12-15K miles on a Pamco with E-advance driving an Accel 140403 dual tower coil powered by the stock alternator controlled by an old mikesXS voltage regulator. I had to replace the brushes (once). I prolly put 5 or 6 pamcos into XS650's. In total had one early e-advance go tits up while the bike was sitting in the shed for a couple years. In the day it was accepted wisdom that running a PMA - Capacitor set up was not good for Pamco longevity. The Cap does not clamp voltage spikes (transients) as well as a lead acid battery does.
Mikes Green monster coils were kind of over the top and may not have been the most reliable. The Mike's cheap dual tower coils were junk, sometimes failing in the box before installation. The primary terminals were poorly supported and would fail breaking the fine wire connection.
I've not put a lot of miles on any PMA XS650's.

 

[650Skull]

Reported problems with the later Pamco's was. More of a resault of Mike'sXS selling reversed engineered Pamco's (as Pamco's), that were unreliable.

Green Monster coils caused a problem with pamco's for 2 reasons, (may have been more??), When/if the spark plug had not been grounded when testing for a spark, or if ignition was left on for to long when troubleshooting.

Another reason for pamco failer in conjunction with PMA installation, was not isolating the pamco on initial start up of the pamco/PMA installation. Any spike would cause the pamco to fail, the green monster coil when used in this situation made for instantaneous pamco failure.

I put a collection of information in a thread, (it's in the Tech Menu), it covers installation and all the tip bits of info good and bad, scattered throughout the site, with a lot of Q and A type posts I copied and pasted.

Installing a 7.5 amp fuse isolating the coil and pamco is important.

The Pamco thread
https://www.xs650.com/threads/boyer-and-pamco-ignition.46859/.