Hi bd,
I haven't run my 641 too much since the high output coil was installed as part of a conversion to 12 volts, but a few years ago I made the same change to my 4-cylinder forklift.1. High output coils draw more current which noticeably shortens point life. Either install an electronic ignition(triggers the ignition with very little load on the points) or plan on replacing the points frequently. Another option is a breakerless distributor. I have no first hand experience with this unit, but the link below will take you to a website that has a breakerless distributor for your 641. 2. The distributor cap may not be able to cope with higher ignition voltage. At the original ignition output it seemed the distributor cap on my forklift might never have needed replacing. With the hotter ignition the cap fails about every 4 to 6 months. The tractor cap is bigger so that helps, but the caps design, and material it is made of, will also be factors in how long it lasts. 3. Spark plug wires that were fine for the standard ignition will either not work at all, or won't last too long. The only option is a GOOD(read expensive) set of high performance wires. An automotive speed shop can supply a universal set of high performance wires that you can make up yourself. The best terminal ends are the crimp on type, but special crimping pliers will be needed for these. Having to spend more for plug wires isn't necessarily a bad deal as these wires usually last a lot longer than cheaper wires. Most of the use on my forklift is short duration. Although the engine is in good shape, has a carburetor that is functioning correctly and adjusted properly, and has a hotter spark plug, we were fouling plugs fairly often. Although the hotter ignition caused some problems of its own, the high-lo is more dependable now than before. The answer to your question depends on whether your tractor really needs more spark, and whether you are willing to either address or live with the points, plug wire, and distributor cap issues I detailed. Good luck...Al English
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