Brewster: My bad, sorry, it may not actually increase crankcase compression ratio at a mechanical level but it pulls the throttle plate close for a better signal at the jets. BRUCE ,just clamp the back side of the carb in a 3or4 jaw chuck and get it centered good then turn it down . your friend should have some good cutters and he can even custom grind a tool to match your shape or groove for the airboot.on some bikes and motors though if you turn the front down and the carb is on an angle the bottom of the float bowl can get real close to the engine cases and touch . this is bad and can cause fuel frothing, which can give you jetting problems or starvation problems.Bruce , is that the RM144 with the jetting problems you had before/ maybe the spring jiggling and vibrating was adding to your nightmare a bit? Husky 250/360 motors with mikuni carbs had the float bowl nut resting on the top of the engine cases , on the later models they had a sort of rubber cushion glued there. I used to :thumb: like to add a reed spacer (CR250 honda) on these motors to add space , it also seemed to give them better pull.Good Luck