Hey crassius, I'm looking to buy a replacement cylinder & piston for a motor that I bought from U-Moto a little over a year ago. You told me about U-moto, thanks by the way, looks to be a pretty good quality motor. I bought the PK Boom. I still haven't used it ( because my other bike is still goin' strong) but I would like to get a spare top end for the PK Boom. Do you know if the cylinder & piston that U-Moto has listed on their website are a DIRECT replacement?