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Ooops, I made this reply to some posts at the first page of this thread without seing that I already had answered. But I´ll leave it here since people are always asking me why I did it the way I did and not like a more traditional two-in-line engine.
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Frank, have you tried to run a four cylinder engine with only three pistons? Long ago I heared about a man who bought an old car with V8 engine that felt slightly "off". The buyer suspected something was wrong with the ignition system or perhaps a stucked valve. He finally put a thin welding rod down the sparkplug hole and ended up in the oilpan... -No piston at all! But that was a heavy slow V8. Removing a single piston from a four-in-line is probably something completely different that never appeared as an alternative to me.
When the idea of removing pistons first appeared to me perhaps ten years ago I thought of it as a way of saving fuel only. My experiences from single- and two-cylinder-in-line engines told me that if I hade chosen to keep the two pistons running in paralel without modifying the crankshaft counterweights I would have ended up with an enginen that SOUNDED smooth but with terrible vibrations.
Earlier in life I had a coupple of small Fiat 126 with a two cylinder in-line engine in the rear. These engines are designed for this like most 2-cyl motorcycle, but there´s no doubt that they still give nasty vibrations. The 126-engine is resting on a soft coil-spring in the rear. I once tried to replace the spring with a common rubber cushion (?) and got terrible vibrations.
A two-in-line two-stroke engine have a 180 degree crankshaft with the pistons going opposite directions. There still is a rocking imbalance but that is smaller than the total vibrations from a single cylinder engine of same size. I have a 600cc 12Hp Kubota diesel that also utilizes the 180 degree configuration. So choosing this for my Fiat engine modification wasn´t a difficult decission.
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