Photo by Genghis
STOCK AND STEADY DOES IT: The Fairbanks Morse magneto served me well on Sally The Bitch. See the spring holding it at full advance?
TIM AT THE SEEDY X-BAR:
“Interesting read, I didn’t know about the screwed tire thing, only seen that on dragsters, what were the torque specs on that bike? As far as the magneto, I’ve never had one and they always seemed a bit iffy to me. Do you think the stock H.D. one performed (or held up) better than the aftermarket ones(Morris/Joe Hunt)?”
If you’ve seen the video of Snow starting his ’69 Sportster XLCH, you know that it took him eleven kicks to start ‘er up. Man, that’s not bad, considering that his magneto’s stuck at full advance. This calls for a thorough dousing with WD-40! If you haven’t seen it, you can find a link to it at the Going The Distance website.
Ideally, these magnetos should be retarded to optimize starting. The retarded position provides a better spark at low revs, and it also mimimizes the chances of the mighty XLCH motor kicking back at ya, and driving your right leg through your hip bones like an inverted jackhammer. Normally, the magneto rotates clockwise to the retarded position for starting the bike, then rotates counterclockwise to the advanced position, which provides a hotter spark at operational motor speeds. The usual arranagement for controlling retardation and advancement, is a cable from the handlebars to achieve this. The push/pull cable is attached to a lever at the base of the magneto, moving it in either direction, with a twist of the left grip on the handlebars. I did it differently to simplify the bike.
If you look carefully at the picture of my ’68 XLCH “Sally The Bitch,” you’ll see a small spring that is attached to this lever on the base of Sally’s magneto. On the other end of this spring is a small hook, which I hooked onto the support bracket of the carburetor to keep the magneto at full advance. If you look carefully at the photo of Sally, you’ll notice this spring crossing in front of the magneto, on its way to the carb support bracket.
By using this spring, I was able to retard the magneto by hand to start the bike, and then advance it by hand after the bike started, and locking it in the advanced position by attaching the hook to the carb bracket. I eliminated the cable system by doing this. There’s that Occam’s Razor again–simple is always better, baby. Just as a sidenote, I eliminated much on this bike by rewiring it. I got rid of the kill switch on the handlebars, by connecting the kill switch wire from the magneto, to an on/off toggle switch that I hung on the bracket on the left side of the bike that routes the spark plug wires to the motor. Now instead of being a kill switch, this functioned as an ignition on/off switch. Simple is better.
With even perfect timing, plugs, points and condenser, Sally would ususally start in cold weather with between 10 and 15 kicks. On occasionally bad days, it might take up to 30 kicks. Very occasionally, She might start on the first kick. When warm she would always start on the first kick with the S & S Super B carb. With the gawdawful Tillotson, she would not automatically start on the initial kick while warm.
The Fairbanks Morse magneto that came on Sportsters like Snow’s and mine, were extremly reliable. As I’ve said in the past, Sally’s never stranded me due to magneto failure, so the question of whether aftermarket magnetos like the Joe Hunt are any better, is a good question. Now, I’m no electrical engineer but I can tell you what I’ve always thought about aftermarket magnetos. A lack of substantive knowledge, has never prevented me from giving my opinions before, so why start now?
The performance limitations of the magneto stem not from design, but from the inherent drawbacks of magnetos when compared to battery systems . It’s no secret that the magneto produces a relatively weaker spark at cranking speeds than a battery and distributor system. Since the Joe Hunt magneto is nothing more than a copy of the Fairbanks Morse magneto, it’s hard to imagine that an XLCH would start any better with it, than with a stock magneto. The longevity of the Fairbanks Morse has also never been an issue. Look at Snow’s bike, “Animal Mother.” The magneto’s 42 years old, and the bike still starts within 15 kicks, and that’s with the magneto frozen in a less than optimum fully advanced position.
The Joe Hunt magneto has a billet points plate which supposedly hold the points in adjustment better than the stock plate, but so what? This doesn’t really produce better performance, per se. I had a single instance in the 17 years I had Sally, when the points went out of adjustment, but that was from the points adjustment set screw not having been tightened enough. What you’re getting with a Joe Hunt magento, is a newer Fairbanks Morse. A label with “Joe Hunt” slapped on the magneto body may get you more admiring glances from bikers standing around looking at your bike, but that’s about it.
The magnets in the Joe Hunt unit are the same size as those in the Fairbanks Morse, so the starting capabilities to me, would be the same for both. Sally never lacked for spark at speed, she ran great, so what are the advantages of the aftermarket magneto? Beats me. There were times after years of owning Sally, that I considered sending her magneto magnets to be remagnetized. I read back then, that weakened magnets produced a weaker field and therefore a weaker spark. But I never bothered having the stock magnets remagnetized, because as far as I could tell, Sally started as well after 17 years of riding, as the first day I bought her new from Harley-Davidson of Manhattan—which was not so good. This “not so good” standard didn’t deteriorate to “worse than not so good,” so why remagnetize the magnets? For that matter, why change to a more shiny, perhaps more prestigious aftermarket duplicate of the original? Didn’t make much sense to me to do that.
It’s always this way: Enterprising vendors offer a “better, newer, more shiny” knock-off of an original part, and the newer, shinier version is invariably more expensive. Meanwhile, a careful scrutiny of the copy reveals a component with the same dimensions and essentially the same parts as the original unit. We are led to believe that somehow, the copy transcends the original’s design limitations, with enhanced capabilities commensurate with its increased price. I don’t think so. Later.