flywheel timing marks and ignition setting

[jakub]

flywheel timing mark is stell ball with some 5UIC lettering but just little bit before there is a triangle pointing outwards, what is it for ?? any idea ??

also what are your expirience with ignition setting, originaly it should be 5 degree before top point but modern fuels burn more slowly so there might be need for more advance, personally I use mostly LPG, with 15 degree advance (5 original plus 10 on distribiutor) engine starts and works beautifuly but lacks bit of power, with 10 degree there is more power but during acceleration engine runs bit unevenly, sounds like misfireing which is obviously not a case since it is accelerating pretty well,