rebuilds

first it will get hard to start, mainly in cold weather and it will lse power slowly, do a compression check
 
depends, if done right and good oil used and maintained ive seen blastys from the 80's with stock pistons running perfectly
 
my theary is if your not a race only blaster, there is no need to rebuild it untell its low on power or wipes out the rings, i think there is a recommended amount of hours before needed a rebuild but, just ride it tell it needs to be rebuilt,

yes you can do it your self 2 strokes only have 14? 17? moving parts unlick what? 400? in a 4 stroke??
if your doing just a top end rebuilt you can do it in a few hours
 
always, always take ur time when doing a rebuild man, it is expensive if you f*ck sh*t up and have to buy a new piston kit because you didn't break it in right or you didn't put something together right, and always use good yamaha oil, my bike has been running yama 2r, i am still on stock bore,rings, piston, its an 02,its all about how you take care of it, you can ride the piss out of it, i do, but mine is well maintained and well looked after, and preventative maintenance saves you money. and everyone knows in times like now every dollar counts