i work for HFT, the old 79cc motors were bored out to 99cc, had the carbs adjusted accordingly and painted black
they have coupons out there that make em' 99$ which isnt too bad at all
when the stock was swapped out i grabbed a 79cc and a 190cc greyhounds on clearence, they havent had blue motors in my store for 6-7 months now
BUT
they probably still sell small water pumps, the smallest gas powered one is 98cc, the interesting thing is that the cylinder is verticle as opposed to the horizontal ones
goodluck finding an underbored one, the new ones are the exact same size and bolt patterns