why do you need to replace a 2 stroke top end?

[quadsrlife719]

on like a dirt bike like a 125 or 250 why do you need to replace the top end every so often?

[rockbase]

the 2 stroke engines seem to need more maint on valves, gear chains ect. as noted below;
get a second opinion!!! unless you rode the bike very hard and long, with minimal or no maintenance. if it were a crf250r i might buy it, but a 450x?? i dont think so.
the "x" model is designed to be more durable than the full race "r" models. seriously get a second opinion
links:http://forums.dirtrider.com/70/6882214/honda-dirt-bikes/top-end-rebuild-after-12-rides/index.html