Nasty Electrical Gremlin

Hey all. New guy chiming in and hoping for some world-class advice, as this looks like an exceptional site.
I've a '74 Commando 850 that I brought back from the dead back in '01-'02 with a near-total rebuild. Among many other things, I re-wired the bike to include a Tympanium voltage regulator and a Boyer electronic ignition. With the help of a few great shops across the country (English Motors in Hanover, PA and Rabers in San Jose, CA), I was able to tune the bike to near-perfection and I enjoyed a few thousand miles of trouble-free service before I had to store the old girl due to health problems.
A few months ago, I finally found time to bring the bike back to life. An oil change, a quick check of valve clearances and a new battery and the bike fired right up and ran like a top. Like a top, that is, right up until the new battery was drained completely.
I'm a decent mechanical guy, but I'm an absolute dunce when it comes to electrical. I can wire from tab A to slot B, but when things go south of cheese, about all I'm good for are a few one-liners. Having said that, I still charged (pun intended) into it.
I replaced the battery, installed a new battery-cut-out switch to replace the one that fell apart when I switched on the power, started the bike, and then cut the battery out of the circuit via the switch. The bike immediately dropped to idle and ran like crap. I did this a handful of times at different engine RPMs with the same result; the engine would hesitate, backfire, spit and snot until I chopped the throttle, and then it would (mostly) maintain idle, but nothing more.
The electrical system is wired in accordance with the Tympanium wiring diagram for a positive ground system - the alternator leads go to the yellow wires on the voltage regulator, the positive lead goes to ground, and the negative lead goes to the distribution post on the fuse block I installed. The battery negative lead goes directly to the same distribution post on the fuse block, and the positive lead shares the same ground as the voltage regulator; the grounds are tightly bolted to the frame. All users/services are fed through the fuse block, and all fuses are intact.
For whatever reason, I convinced myself that I somehow fried the voltage regulator when I changed out the battery, so I ordered a new one and installed it, and experienced the same problems. I re-installed the (original), and put the new one on the shelf for a future build. Knowing that the bike runs fine on battery but hardly runs on the alternator, I figured that the alternator had finally given up, so I ordered a new rotor and coil and installed these. With fresh fuel in the tank, I fired the bike up on battery, then cut out the battery and experienced the same problem. At this point, I figured I had a broken wire, so I ran continuity checks on all of the leads running from the alternator to the voltage regulator, and from the regulator to the ground. Nothing obvious has shown up, and at this point, I'm out of ideas, and hoping for some advice. Thoughts?

Put the leads from the alternator on youre tounge with it running to see if its produceing any electrickery . :? :lol:

The wires sometimes crack with all the hot oil down there inside . Id assume the rests ok .And start there .

CRC or WD 40 into switchgear , & or blow out with compressor . Visual Inspection . Clean Contacts & remove debri ,
Little electrical contacts after 40 years often need cleaning .

Its all perfctly logical . :mrgreen:

Check all your connectors and the ignition switch, kill switch anything else in line for high resistance. Best way is to measure voltage across connectors/switch while running. You will need a quality voltmeter that can read less than .1V or if it can read less than .01 ohms, but volts are the cat's meow.

Remember this is an old bike and the connectors and switches may be dirty. If you have low voltage on your EI and coils, it will run like crap.

Dave
69S

Thought Boyer ignitions don't run without a battery and run poorly below a certain voltage.

Sounds to me like a bad capacitor. Jim

Yea , theres been five thousand complaints in the last three weeks about Boyers and Flat Batteries .

Therefore CHARGEING Circuitry and Componentry , one of which is mentioned above , would be the first order of investigation . With one of those little electricity things with the dial on it (and a battery ).
We assume youve been caught before with the old tonge on the ellictricity trick . Then theres the Magneto chain , party trick . Can lead to fainting were told .

Spars 3 phase instructions say to not cut the motor by disconnecting the battery. Damage will result. Don't know if you've a sparx or if that warning applies to all alternators

Oh, you fellas are all a bunch of comedians!!! Hahaha I like this group already :wink:

I'll check and clean connections, but the ol' man found a write-up today on another site that mentioned something about pulsing from the alternator causing the electronic ignition all kinds of heartache. The "fix" is to load the system, ie introduce a battery or just turn the doggone headlight on. I'm going to button everything back up and try this first - because it's nice n' easy to do - and see what happens. If that fails, I'll get to cleaning contacts. I have one of those fancy meter-thingies... it makes fun beeps and has pretty colors... I might turn it on for inspiration while I'm fiddling around

I'll let y'all know what happens. Fingers crossed that all hope ain't lost...

Yeah, ok, so the idea of loading the system via the headlight in order to absorb power pulses flopped like a pregnant polevaulter. I'll work on cleaning up contacts in the switch gear and post an update later. SAD!!!

Comedians? Hey, after you've put everything on a Norton at least 3 or 4 times, you get a sense of humor. Yes, a battery is a very large capacitor and will suppress all sorts of nefarious distractions in the electric circuit. You didn't mention that the battery was not connected, as I remember, but my mind is very short, in other words, not in this country very long distance.

Good luck and come back.

Dave
69S

It's more complicated, but why not run the alt/battery negative leads to the fuse box and the hot post on an ignition switch and use the stock loom and swtichgear to control relays that supply power the important things like ignition, lights, ect; which could take direct current from the individual fuse panel outputs? It would be direct separately fused power.

Could someone get away with disconnecting the battery if you have a capacitor, running electronic ignition?

I always thought the whole purpose of the capacitor was to store enough juice to start the m/c with a low battery
with the standard points ignition.Please enlighten me.
YING

I ran my 69 for years without a battery, just the MC2 and points. However, even though it produces a spark without the battery now, it won't start without the battery, I can only assume the rotor has lost some magnetism and is just not putting out enough. It will run without the battery once started, but not smoothly, but that's with the Pazon which is sucking about 3-4 amps even at idle.

Dave
69S

Nasty Electrical Gremlin- Follow-Up

Evening, fellas.

Got the old Commando up and running on Sunday afternoon in time to take a nice long (for me... big guy on a lil' bike) ride. Here's how it played out -

I had nothing left to check. I replaced everything, ran continuity checks every which way to Sunday, and didn't know what more a guy could do. I gave up on it for the weekend and spent my time in the office catching up on some proposal work.

At noon on Sunday, my brother called and asked where I was; he was sitting in my driveway after riding his '71 Bonnie over to the house. I left the office and ten minutes later, was admiring his new large-diameter (forgot what size he said the pipes were) exhaust system. As it was in the 60s yesterday and sunny, and as it's February here in God's country and by all rights should be nut-shrinking cold outside, I decided I would ride back to his place with him - a nice easy 25-mile ride. I rolled out the RC51 (it's one of those funny-looking butt-in-the-air new-technology high-school kid wheelie-machines, for you "older" gents) and started giving it its pre-flight check. My brother looked at me funny... and then insulted me, saying I didn't have the stones to take the Norton out alongside his old all-stock Bonnie. I told him I wasn't done "trouble-shooting", even though I'd all but given up on the stupid electrical problem and was giving serious consideration to some new Norton "yard art". He said it served me right for running all of those fancy electronics. Prick.

So oI jumped on the phone with the ol' man - a huge, vast, oft-tapped wealth of knowledge of all things, well... all things - I was told I'd done all of the trouble-shooting a guy could do and he suggested I do a final voltage check of the battery before starting the bike, after starting at idle, and again at higher rpm. Static reading on the battery was 12.35 volts. With the engine at idle, readings were all over the place from a low of about 8 volts to a high of about 11.5 volts - certainly not confidence-inspiring. Once engine speed was increased to about 2,000 rpm, voltage levels jumped up and settled out at about 14-16 volts... the battery was receiving a charge and the engine was running smoothly. I made a mental note to just resign myself to the fact the bike would have to run with the battery on at all times, and we lit out.

Lesson learned, I suppose - the combination of an electronic voltage regulator and Boyer electronic ignition absolutely requires the use of a battery in the circuit - or, perhaps, at a bare minimum, some sort of capacitor. I don't remember ever having problems with this before, but then, there's a lot about my mid-late 20s that I don't remember. Stupid Miller Lite.

If I can figure out how, I'll post a few pics of the ride - enjoy, and thanks, men, for all of your suggestions. They may not have directly helped, but a dialogue almost always leads to the final answer.