what you have to understand is crankcase volume , just because you put a bigger crank in a smaller crankcase it doesnot mean its going to make more power as the bigger crank takes up to much space and then you cannot move enough air threw it . I play with lots of these kind of things then just scrap them once I'm finished and they never leave my place , Prefect saw is I put a 3120 crank in a 181 just to see what I could get , that took abit of lathe work on the crank to make it fit and it ran but not as good as a stroked 181 crank to 42 mm , I could not burn near the same amount of fuel threw the motor with the 3120 crank, used the same jug