Dear coronabob,
Kindly refer to post #5,
"And for a successful start system, we need to design it to have at least twice this amount of torque i.e. at 57.8Nm."

Without taking into account the internal friction of the engine components and inertia forces of those pistons, rods and crankshafts, the negative torque produced by the engine to resist rotation is only 28.9Nm. If we apply only 30Nm of rotation torque, we will be able to rotate the engine already. However, in order to be 100% sure, we double the amount to 57.8Nm and this is the rational of post #5.

With regards to motor and gear efficiency factor, i left that one out. The reason is simple, i'm trying my level best to bring interest to many in developing RC DIY. If we include too many techs, it will kill the interest... And because of this details not being included therefore doubling the requirement (as per post #5) will definitely do the job.