[technicalities]

[TECHNICALITIES]

GORDON H. JENNINGS

SINCE PUBLISHING the recent article about supercharging motorcycles, we have been getting a lot of mail asking for advice regarding the fitting of some particular supercharger to some particular motorcycle. We would like to help, but the only way we could give really worthwhile advice would be to first do the job ourselves, and then pass along a step by step description of how the installation was made. Obviously, this is not possible. All we can tell you is that the drive sprockets, or pulleys, should be as close together (from center to center) as possible, and that the manifolding between supercharger and ports should be as short as possible (the buffer chamber can be bulged out to the side).

When this column was initiated. I promised to pass along the word on (among other things) any interesting new' products. One such product that has come to my attention is a VHT (very high temperature) enamel from the Spercx Corp.. located at 1927 Pontius Avenue. Los Angeles. Calif. Spcrex's VHT enamels are available in brown, black, gray, white, yellow, red. green and blue, and will withstand temperatures up to l()00°F. continuously. For short periods, the stuff is unaffected by 1200°F. and it will also withstand such corrosive agents as salt spray. The VHT enamels are also very resistant to chipping and have excellent dielectric properties — which in layman's terms means that they are good electrical insulators. The uses that immediately suggest themselves are on exhaust pipes and cylinder blocks. Best results are obtained by baking the enamel (which will occur automatically in the applications just mentioned) but it will also air-dry reasonably quickly. Incidentally, if you paint a frame with the stuff, make sure that any “ground” wires are contacting the frame and not just the paint — it is an insulator, as I have said.

Those who own or have ridden HarleyDavidson's Sportster may have noticed that starting can be a problem. The Sportster's engine is willing, but unless you run it through very smartly, it has a tendency to kick back. Now while many motorcycles do this, none of them put quite as many cubic inches into the backlash as the Sportster, and that creates a problem. Fortunately, there is a solution: Webco has a kit that provides a manual retard for the magneto — taking all the excitement out of starting the machine. The kit consists of a mounting flange plate that permits a few degrees of retard (by rotating the magneto) and a handle to pull the magneto housing around. No wires; no cables, Just a handle. An automatic lock accurately locates the magneto for correct running advance w'hen the handle is pushed back to the “run” position.

Speaking of ignitions. I would like to get in a few words about the latest developments in Triumph’s energy transfer system. As many Triumph owners are doubtless aware, this type of ignition has been something less than trouble-free. Indeed, many (if not most) of the racing fraternity have changed their Triumphs over to some form of conventional magneto or battery and coil system after a few frustrating bouts with the energy transfer system. People who ride touring Triumphs have frequently been plagued with a mysterious “miss” that appears only in the medium and high speed range. Usually, this miss will be due to an ignition problem, and even when it is not. the ignition system's reputation virtually assures that it will be blamed. In fact, service problems with the energy transfer system (in Triumphs, and other makes of motorcycles as well) have been so numerous that Triumph has been moved to renaming this type of ignition “AC magneto,” which is a tribute to the flexibility of the English language but doesn't alter the facts.

Actually, there is nothing fundamentally wrong with “energy transfer” ignition — so long as those who must repair and adjust are in full possession of the pertinent data. The problems are created when everyone is groping in the dark.

The energy transfer type ignition system actually is a form of magneto, but its various elements are sprinkled all over the motorcycle, instead of being grouped into a single case, and unless all of these elements are working together, there is a very weak spark or none at all. With a conventional magneto, it is possible (through misadjustment) to get the spark at the wrong time, but there will be a spark. With an energy transfer system, the spark can simply disappear — even though all of the wires are connected properly and the coils, condenser and breaker points are in perfect operating order.

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An energy transfer system consists of an AC generator (with a rotating magnet and fixed generating coils in all existing examples) that is wired to high-tension coils and the breaker points. This setup differs from a battery energized system in that the required primary voltage is not alw'ays available. A battery pushes out a steady voltage; the AC generator delivers it in pulses. This is because the AC generator is producing electricity by sweeping a magnetic field through coils of fine wire, and with 6 coils and a matching number of poles on the rotating magnet, there are 6 distinct pulses with each complete turn of the crank-mounted generator. Of course, the pulses are strung together, in sine-wave form, so that output voltage drops to zero only for an instant between peaks, but it is equally true that each pulse is at its voltage peak only for an instant. At that instant the ignition breaker points must open. If the points break when a pulse is just forming, or has faded nearly away, the voltage to the coils will be too low to produce much of a spark.

Now then, because there is no direct link between the points and the AC generator. it is entirely possible to have the voltage peak completely out of phase with the breaker points. One might think that any competent mechanic could get them working together, but that is not the case. It is easy enough to set the points so that they break contact at the proper time relative to the engine; you can bring the pistons up to, for example, 40-degrees before top center with a degree wheel, and then adjust the breaking of the points with a light. Unfortunately, there is no tool in the average mechanic's box that will show where the AC pulses are occurring.

Due to all of the difficulties that have been experienced with the energy transfer ignitions, Johnson Motors, the distributors for Triumph in the western United States, have made a complete study of the system, the problems, and have at last developed a method for making things right. They recommend that the tuner disconnect the AC generator and make a temporary connection with a 6-volt battery (two batteries when the machine being tuned is a twin). The machine is then started and the output from the AC generator checked with a voltmeter. If it meets specifications, then the ignition points can be timed with an ignition "strobe" light and a degree wheel. The degree wheel and related hardware for bolting the wheel to the end of the breaker cam — and a little device that will enable the tuner to locate top dead center — can be purchased from Johnson Motors.

Then, after the ignition is timed, the indexing of the AC generator’s rotating magnet can be checked. With the engine turning about 3000 rpm. firing should occur when the rotor’s pole pieces are aimed almost directly at the coils in the stator. We say "almost.” because the indexing of the rotor should put the "leading” edge of each pole piece 1/16" past the “trailing” edge of the adjacent coil core piece. That is where the AC generator will he producing maximum voltage. If it is not indexed to that position, then it will be necessary to slip the rotor out until it is free of its driving pin. turn it until it is indexed properly, and give it a light tap with a hammer so that the pin will mark the back of the rotor.

Finally, drill a hole through where the pin made its mark and bolt everything together. The last step, which will really make certain all is well, is to disconnect the batteries and reconnect the AC generator into the bike’s electrical system, after which you can again start the engine and check with the strobe to see if the spark occurs when the rotor is properly indexed. Obviously, the engine will start, you will have hit it fairly close, but the strobe will reveal exactly how close.

If you want a complete set of instructions regarding this procedure, with voltage levels for the various stator coils, write to Johnson Motors, 267 West Colorado Blvd., Pasadena, Calif. They have service bulletins printed for their dealers; ask for bulletins 4-64 and 5-64. •