Self starting Commando

There have been a couple of references to bikes self starting when the piston and fuel is present in the correct ratio and position. Just supply a spark. I'm guessing that the piston would have to be past TDC on the compression stroke for the spark to ignite the mixture and send the piston down the bore. With a 360 degree twin the problem as I see it is the compression on the second piston preventing the complete cycle to continue. Is there an optimum position on a Commando engine for the self ignition process to work? Here's my thoughts. position the crank past TDC, valve lifter on the opposite cylinder to reduce load until after single cylinder start. spark the ignition, engine starts on one cylinder, disengage the valve lifter on the other cylinder. Ride off into the sunset. What am I missing? (apart from a few brain cells)

gripper said:

engine starts on one cylinder, disengage the valve lifter on the other cylinder. Ride off into the sunset. What am I missing? (apart from a few brain cells)

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Well i'm not sure what your missing but i think my bike is missing a valve lifter. I have looked all over it an can find one.

Kicking it would be quicker than all that carry on.

In 1965 my mate had a C11G and it would self start, we all thought it was possessed. Years later the penny dropped, early Lucas ignitions spark when switched on. Clearly the old C11G had a good combustion seal was just past top dead and pop off she would go.

Dave

gripper said:

With a 360 degree twin the problem as I see it is the compression on the second piston preventing the complete cycle to continue.

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If there wasn't sufficient energy in the crank to bump it over compression after one revolution then it seems unlikely there would be enough energy left after two revolutions?
Also the energy imparted from the second piston's power stroke would help spin the crank over the next compression (and so on) but by decompressing the second cylinder that additional power stroke is lost.

Doing a bit more digging, it looks like you need a squirt of atomised fuel and a spark into the combustion chamber and probably more than 4 cylinders.

Looks like a job for Jim Comstock to solve. :mrgreen:
Tom
CNN

Wouldn't that be cool, just turn it on, and it starts. That would impress someone, especially me.

Too much coincidence. BOUNCING off compression is one thing... from a standstill is quite another. I'm sure it's happened, but a lottery odds coincidence.
We start our snowmobile two-strokes backwards by bouncing off compression just as the engine is stopping. A very cleverly designed second ignition pickup lights the fire at just the right moment... brilliant.