well in the last two weeks i have played a lot with my bicicle with 4t stroke motor... i´m going to work everyday with it now and i´m saving some money on gasoline...
i found that this motor is one cilinder around 48cc and has a compression ratio of 6:1
and the recent studies i made i have learned about the advance on spark ignition and fuel mixture burning speed...
i found some slow motion transparent motor making a good picture of what is all about..
basically the spark does not occur at the tdc point it rather is advanced happening before the tdc because the fuel is not prety fast enough to burn and create maximum pressure at the high point of the piston... this is where the higher efficiency lies on...
so before the piston reaCH the tdc point or the maximum compression the spark happens... from 12degres at idling and up to 30 degrees before tdc at acceleration
distributors have mecanical or hidraulic means to create this advance according to rpm
https://www.youtube.com/watch?v=e0zFM65jTzIhttps://www.youtube.com/watch?v=p_P1-2octb4