Yup, John, as you said, 1 & 4 are paired to fire together, 2 & 3 are same pairing, 180 degrees later, so, TDC 1/4 fire, 180 degrees later, 2/3 fire together, then back to 1/4, etc. In essence, two "Twingles, 180 degrees apart. If these pipes were to work to make torque, the pairing, one would think, would be 1/2, 3/4, not 1/4, then 2/3.
The only thing I heard from Von Desco (our nickname for him) was he was seriously thinking about changing the firing order, 1/2 together, then, 3/4 together. Then, in theory, these pipes would have the right pairs feeding them. They were designed to help with torque, because the streamliner was a lot heavier than a TZ bike, but, it had TWO of these engines in it.
You'd have been very surprised at all the screwball ideas that came up back then, some were hilarious, some down right scary. Like the Laverda 4 stroke inline 3 cylinder, first iteration had 1/4 pairing (switching back and forth at TDC, one firing, one on overlap, swap ends the next TDC of that pair), with the center cylinder 180 degrees apart. Second design was much like the Yamaha 750/850 triples, 120 degree firing, with one complete crankshaft rotation a dead player.
Like you said, "interesting".
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