Really interesting Robert.

I don't understand why 4-strokes are often lighter than 2-strokes. From what I understand, a 4-stroke doing only one fire every 2 revs mean a real big bang (needing here more solid parts) as for 2-strokes, a smaller less efficient fire every rev (less stress to parts so smaller are required). Just wondering how can an engine with more than twice the parts and higher stresses involved end up lighter.