Just got done from a weekend of riding with this engine and the upgraded VM26 carb. I put the engine on a Xmotos rolling chassis that I bought. Despite my fitment issues due to my frame being a slight bit different then the typical SSR/Piranha/Pitster frame I got it installed and broke in with out any issues. After breaking it in all I can say is WOW! I went toe to toe with both my friends on there SSR140's and they never stood a chance. From a roll in 4th gear I could hang with my buddy on a KX125 until I just about tapped my bike out. If this thing had a 5th gear it would have been a real challenge for him to get away from me. I cannot say enough good things about this engine. 2nd gear rolls on pavement pulls the front tire right off the ground while sitting down.