Originally posted by 3D Joy
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.
Simple: an engine built to do 10K rpm can be built much lighter than one built to do 17K.
The "bangs" on a four stroke aren't bigger, they just last longer... Combustion strokes on a two-stroke are very short and combustion power has to be transmitted to the system in a very short period of time. Combustion strokes on a 4-stroke typically last 160-170 degrees, so there is much more time to transfer power (hence: more efficient).