Thanks for the feedback. I'm going to give it a shot, the setup is a freebie sitting in a box on a shelf. I'll have the head resurfaced and o-ringed and re-ring it, bolt it on and see what happens. More or less I'm just curious how the 310 performs, if I was going to spend money on a big bore cylinder, it would not be a 310. Sphynx or Puma or even the ESR four stroke killer set up intrigues me. Always on the hunt for a 250r setup to keep up with my 500's.