(If you don't want to read my less understandable guide then you can just click these links to download sum self-starting piston engines straight, v, big boi )

cycled pistons can be used to make engines/motors by using the cycle feature, but (as far as I know) can't be offset by any angle other than 180 degrees (push or pull)

but we can use SimpleFunctions™ like sin or cos, and sum function to make cycles and offset them.
ex.
sin(sum(INPUT) * SPEED) or cos(sum(INPUT) * SPEEDMULTIPLIER)
If you want to make it self-staring you'll want to rotate another piston by 90 degrees or advance the cycle by 90 degrees (one piston is using sin and the other cos)
ex.

or

(the two cranks are connected to each other)

the problem here is the piston using the cos function pushes or pulls from the start without input so we shall put a minus 1 in the input
ex.
sin(sum(INPUT) * SPEED) and cos(sum(INPUT) * SPEEDMULTIPLIER) - 1
or
sin(sum(INPUT) * SPEED) - 1 and cos(sum(INPUT) * SPEEDMULTIPLIER)
Now just put an angle to the other piston
ex.