why do you have to rebuild your 2-stroke motor after a certain time what does it do that a four stroke does not. people with four strokes do not do new top ends on them. my dads boat motor is 2 cycle and it is 11 years old it's still going strong...

 

2 strokes do a couple of things that 4 strokes dont do. First every down stroke of the crank is a power stroke compared to every other stroke of the 4 stroke. This will cause some more wear on parts. Also, they rev alot higher then 4 strokes and that adds to it also. 2 strokes last plenty long if they have clean air and fuel. especially the bigger bore 2 strokes. Racers (2 & 4 stroke) constantly rebiuld their motors cause they play for money and are extremely hard on stuff. Ya cant win on a busted bike. 4 strokers do rebuild their top ends, they just wait longer cause its going to cost em alot more :-) later!