well i was thinking of boreing out my blaster its stock now (66.0mm) how much over stock can i go , yamaha dealer told me it would cost me around $300-400 to get it done not including a piston or rings , but i can get a vito BB kit online 4 $450 and it has every thing needed to work , if i bore it out would i have to rejet and are the BB kits worth it ?????