Power Boxes and Ignition Boxes

- by Pete Snidal, B.E. (Backyard Engineer) (C)1999

I guess it's time for a FAQ/Story for the newbies, about replacing electrics with after-market stuff on our bikes. This may take a few minutes, but it's a snowy Saturday morning, and I have the time, so here it is for those who care:


The Power Box replaces the rectifier and voltage regulator combination. The rectifier is necessary to take the pulses going in only one direction from the alternating current supplied by the alternator - AC to DC, which is necessary to charge the battery. (Suck-Blow-Suck-Blow fills neither balloons nor batteries.) The regulator section limits the maximum voltage to one which can be stood by the lights and any other voltage-sensitive equipment which may be in the system. (radio, tape deck, other electronics, etc.)

Not having hands on and Indian Enfield, I can't say what they use for rectifier/regulator, but I know that Lucas used a Selenium rectifier and a Zener Diode regulator. Both of these were introduced to bikes on the Triumph Speed Twin in 1953, and as such can be considered to be Pretty Old Tech as electronics go. The Selenium rectifier, although a vast improvement in portability over its predecessor, the diode vacuum tube, was improved upon considerably, in terms of efficiency, by the solid-state silicon diode, which was readily available by 1960, although Lucas didn't seem to notice, and probably, either did IE. Ditto for the series regulator chip, as opposed to the Zener method of voltage regulation. The Zener can be duplicated by shorting the circuit to ground whenever the voltage gets too high. Crude and low in efficiency by comparison.

The Tympanium Regulator/Rectifier and the Boyer Powerbox are a quick and relatively inexpensive way to replace and upgrade your charging system, yielding more efficiency which will translate directly into more current for such things as a halogen light and also into greater reliability - dead batteries are such a drag! It is difficult to think of a reason not to replace your regular system with either of these, or equivalent. If money is a problem, you can replace your rectifier with a Radio Shack part - look it up in the catalogue - for about five bucks. The regulator is a little harder to do, but the Zener is not the weak spot in the stock charging system, the Selenium rectifier is. So either way, a little tuning here will yield solid dividends.


A capacitor acts, over a much shorter time period, much like a battery - it takes a charge of electricity, and will hold it until a low resistance is presented to it through which it will then discharge. A good nerd trick, done in most electronics courses at one time or another, is to charge up a cap with some mild voltage, like 110 say, and then throw it to your victim, saying something like, "Hey, Harry; catch!" He of course grabs the thing in midair, and gets a jolt. Ha ha. In extreme cases, you could probably charge a suitable cap with 800V or so and do him some real damage, especially if he managed to get one pole on each hand. A small cap, however, with a fairly small voltage, will only teach him never to trust you again. But that's enough to tell you what a cap will do.

Caps come in different capacities, also like batteries, and in different voltage ratings. Generally, the larger the cap, the larger the capacity. (Capacitor. Capacity. Hmm, this is starting to make sense!) Here's how they can help you with your bike's electrical system. Let's say your battery is dead or really low. When you kick it over, the alternator will make some small amount of electricity. Oftentimes, if this small amount is charging a capacitor, the cap will then give enough of a jolt to the coil to provide sufficient saturation to make a spark or two when the points open. Furthermore, adding a cap will "smooth" out the pulsating DC provided by your rectifier, which can be a help in the case of running electronics, if this is a consideration. The battery of course provides this function, so the cap doesn't really make that much difference, but it will in the case of starting with a dead battery - the difference between go and no-go, in many cases. I found this out in a practical way when I added a cap in an attempt to smoothen out the wild waving of my ammeter needle. It didn't make any difference, but one day when my battery was so dead it wouldn't even light my parking light, I found, to my amazement and total delight, that the thing started anyway! What a bonus!

The cap I used was just an old radio power supply part, rating was 20VDC. The capacitance? I don't remember; it's about 4 inches long (that's four times the width of your thumb for our European neighbours) and about 1 3/4 in diameter. Just wire it in parallel anywhere in your system, + to + (ground, usually) and - to -.


On the other hand, there are also the "Magic-Boxes" - such as the Lucas Rita or Boyer Box ignition conversion. These have dubious recommendations. For one thing, they both require a specific minimum battery voltage to make a spark - a voltage generally higher than that required for the standard points ignition to fire. This means that in many cases of low battery, the "magic box" won't start it, but it would have if you'd left the point system in place. Problem #1.

Story time. I was camping on the tip of the Baja Peninsula one winter, back in the early '80's. I noticed out the window of my van one morning some people pushing a motorcycle around the area, apparently attempting to start it. I also noticed that the bike, a new Y*ha, had BC plates on it - the owner had apparently ridden the thing all the way from Vancouver, - it was covered with camping gear - and now it wouldn't start.

No problem. Your humble correspondent, Mr. Motorcycle, Dr. Bike, strolled out and offered a little help. First, he noticed that they were trying to start it with the lights on. "Hey," I says, "you might have better luck with the light turned off - more juice for the ignition that way."

"How do I do that?," enquires the new biker. I have a quick look at the controls, and discover that there's no way. When the ignition's on, the lights are on, and that's that. Since the light was burning fairly brightly, I concluded that there was no point in disconnecting it, and we went to square 2.

"Well," says I, "You've pretty well determined that it isn't going to go without something more than pushing it up and down the road all morning. Want me to have a look at it?" They indicate that this might be a reasonable alternative, so I then say,

"Where's the points on this thing?"

"Huh?," inquires the happy new rider. Further conversation elicits that he just bought the bike less than two weeks ago, and has ridden it straight out of the winter fog to the most southern place he could go. And he prepared by buying a service manual, so I was able to assure him that, although I hadn't been paying much attention to Y*ha development lately, I'd be able to make it go for him.

It turned out to be a (excuse me) totally pointless endeavour. A reluctor in there somewhere, and instructions in the manual for troubleshooting ignition. Thank God. I thought at first. The instructions consisted of a carefully-drawn chart of which black boxes to replace in what order, so as not to burn out a good new box by putting it in circuit with a fried old one. The advice - to dealers - was just to go to the parts shelf and start replacing boxes. To the owners, it was simpler still: take it to the dealer.

Since the nearest Y*ha dealer would be in San Diego, some 1200 miles north, and since the bike was brand new, and possibly one sold only in Canada, the best-case scenario was finding someone with a pickup with space in back for bike, and space in front for biker, and catching a ride back to San D. Period. Worst-Case was having to go another 2000 miles north to Vancouver, although at least he'd be able to ship the thing and take the bus home. Expensive though. As it was, he stayed for a week or two, and then began looking for someone with the proper qualifications, and eventually went off up the road with a couple on their way to San Diego. Good luck, bud!

A few years later, I found myself stranded in another town on the Baja, about 40 miles from where our bus was parked. We were on our '71 T100, with the points ignition, fortunately, still in service. It took the spare set of points I had in my toolbox to get me running again. Wow! Scarey! - I almost thought I'd have to go to el partes and buy a 12V coil - any kind would get me home. Was I thankful I had points ignition? If you'd seen the vultures standing around waiting for me to leave that bike and hitchike to where I could find a pickup truck to rent, you'd understand why - there are lots of gringo bikes on the baja being ridden into the ground by people who couldn't possibly have built them - lots of trick parts, etc - clearly a "gringo bike." Often with the remains of 5 year old California plates hanging off the rear fender. Not likely, shall we say, legally purchased and imported.

Since it is required to discard your regular points setup in order to install either the Boyer or the Lucas Rita, if you find yourself stuck on the road with an ignition failure, and it isn't your coil (a standard car coil will get you home) your only alternative is to replace the ignition unit. With points, at worst, you would replace the points. Occasional inspection will usually give you plenty of warning of impending points doom, but solid-state electronics just quit one day. So your only hope at a time like that is to be able to whip out your spare ignition unit and flip it in there. Not much difference here, except that the ignition unit is over ten times the price of the spare points set - and it takes up a lot more room in the toolbox!

There is little if any quantitative difference in performance between points and ignition boxes, regardless of what the believers say. Yet it seems that many newcomers to the Brit motorcycle scene trample one another in the rush to embrace the magic of the Solid-State Ignition Box. If one were available that left the points in place (CD ignition systems which give hotter spark and yet reduce the points current to almost zero were the first ones on the market) I might be inclined to give one a try, but never having had any trouble with the much simpler and ever-so-much easier to fix on the road points system as supplied, i also might not. But I would only take my points out of there if I had the money to buy TWO boxes.

The "Far-Out" Argument

There's another argument against magic boxes, and that's the EMP one. Electro-Magnetic-Pulse, from atomic explosions, UFO's, police helicopters, or just research hijinks from some military-industrial player or another can take out solid-state electronics. This would still take out your charging system, (hmmmm. I wonder if it kills selenium rectifiers?) but with a points system you'll still be running. I know this last argument is a bit controversial, but I have reasonable and probable grounds to believe etc., although it's not a very serious consideration. Still, why not be prepared? Although I must admit I'm not anticipating any UFO attacks in the near future, it's just another argument against over-technologizing your dinosaur.

Pete Snidal, Grand Forks BC Canada,
Save Big $$$, Breathe Cleaner Air * www.angelfire.com/biz/snwvlly/ *