crf138 said:ttr's are 4 stroke trail bikes not really ment for racing, all though if you get one and you end up planning on racing you could start going with som upgrades like a bore kit and some BBR upgrades.
if your planning on just messing around and not racing i would go with the the ttr becuase its a reliable bike and there not close to as mutch work as there would be with the 2 stroke yz which is more of a racing bike and with a yz comes alot of work
XRpredator said:TTR = 4-stroke play/trail bikes
YZ = 2- and 4-stroke motocross bikes
glad I could help :)
everybody's pal,
Pred