i think you already commented on my mbx10 with 212 install (on that page) but you can fit one in there if you change the intake and exhaust which will both contact the upper portion of the frame beneath the seat. I wanted to keep the engine stock on mine which is why i lowered the engine plate. there is an adaptor plate you can buy to mount the engine on there with no welding. it's an easy upgrade and well worth it, I dont understand how someone heavier than 50lbs can stand to ride the stock mbx. good luck