Dont know why but I keep losing my posts they just dissapear, try again, I need to know if the gap between the fly wheel and the coil is critical on the homy 25cc, if so how is it set, Thanks, Joe

I posted an answer that got lost also.
The gap matters, and should be as small as possible without the parts touching the flywheel.
I use a postcard inserted between coil and flywheel before I tighten the coil to the engine. After tightening the coil fasteners, often the gap has become smaller than the postcard thickness, and is just right.

The airgap space has a direct control over the firing point of the spark in degrees. Not a massive amount, but noticeable on a hot ,dry day with low octane gas.

I think the lower humidity (more oxygen in the air) has a larger influence on too low octane fuel than the 0.01° timing change due to a slightly different gap. The higher oxigen content will have a larger combustion pressure rise, and consequently will knock (ping) when using too low octane fuels. With the right fuel, timing can change by about 5 degrees without you noticing any difference at all.
I.E, full power is there at about 22BTD, until up to about 30BTD, when the engine starts running harsh. Exact timing for these criteria may change a bit due to compression ratio and/or squish design, but these are the general values for well designed engines.

Gentlemen, thank you very much, this is my first conversion and I am gathering all the information I can get so I don''t mess things up, have any of you done one if so do you have any pics or useful tips. Cheers, Joe

I think you will find the information I gave quite usefull, if not at the moment.