I didn't feel all that much going to the 240 kit on my wife's Blaster, but I have another stock one to finish soon then we will race them to see. I have been told that the stock carb is really holding me back on the 240 kit too.
if your on a budget it's say spend your $$ on a 3mm crank before a 240 cylinder. the have the stock jug ported for the 3mm setup.. then if you decide to go with a big bore later is can be ported for the 3mm setup also.. if you buy a big bore cyl now and port it and then decide later to go with a stroker.. it may have teh transfers cut too high to use a 3mm crank without machining the bottom of the cylinder and maching the difference in the head.. go stroker first.. then big bore..
Along with the 240 kit you will need a good exhaust, bigger carb, V3 reeds, Kn filter, beefier clutch..........Alot more than just spending 500 and change on a kit that "claims" a huge power gain.