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I have a fixed-position magneto in my 1964 Sportster. While I'm still a ways off from starting it, I'm keeping my options open as to whether or not to install the 1965 and later advance plates beneath the magneto. My experience is that some fixed mag bikes start ok and some are a bear on the (already-damaged) right knee. I completely rebuilt the mag and then sent it to Dave Shaw at Morris Magnetos who went through it as well, re-charged the armature and tested it. So I know it has a strong output and that potential magneto-related starting problems are now circumvented. But a lot of fixed mag Sportsters are prone to kick-back when starting, even when using the kill button during the down-stroke. Furthermore, the kicker gear setup on these Sportsters was woefully under-designed. Hard starting XLCH's always resulted in slipping ratchet gears (again, the right knee).
I originally mached-up the advance setup onto the motor but hit the often occurring problem of geometry. Depending upon which gear engagement I used, with the motor in the firing position the mag would not move in (clockwise) enough to offer significant spark retard, as it hit the push rod tube. Conversely, after adjusting its engagement in the cam gear it would move out far too much when advanced and would hit the air cleaner, even when using four carburetor spacers, which in itself is wrong. I also tried several different drive gears (OEM and aftermarket) on the magneto shaft but all were cut almost exactly the same and offered the same result. Rather than deal with a solution at the time, I simply installed the fixed mag setup as that's what the bike came with. The fixed plate actually sits slightly lower on the cam cover than the advance setup and the mag now misses the air cleaner (by just a little) with the correct number of carburetor spacers (3). However, I'm now re-thinking this decision; if its a hard-strrter I'll have to switch to the advance setup.
As I see it, the solution to the above is to rotate the differential timing gear on the end of the camshaft. I'm thinking that the gear would have to be heated (not too hot!) and slid while hot. Because I've never done this before, I'm hoping that one of you has done this and can offer some guidance.
Thanks!
I originally mached-up the advance setup onto the motor but hit the often occurring problem of geometry. Depending upon which gear engagement I used, with the motor in the firing position the mag would not move in (clockwise) enough to offer significant spark retard, as it hit the push rod tube. Conversely, after adjusting its engagement in the cam gear it would move out far too much when advanced and would hit the air cleaner, even when using four carburetor spacers, which in itself is wrong. I also tried several different drive gears (OEM and aftermarket) on the magneto shaft but all were cut almost exactly the same and offered the same result. Rather than deal with a solution at the time, I simply installed the fixed mag setup as that's what the bike came with. The fixed plate actually sits slightly lower on the cam cover than the advance setup and the mag now misses the air cleaner (by just a little) with the correct number of carburetor spacers (3). However, I'm now re-thinking this decision; if its a hard-strrter I'll have to switch to the advance setup.
As I see it, the solution to the above is to rotate the differential timing gear on the end of the camshaft. I'm thinking that the gear would have to be heated (not too hot!) and slid while hot. Because I've never done this before, I'm hoping that one of you has done this and can offer some guidance.
Thanks!
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