how can you be so sure the engines fine? have you checked compression, sparks plugs can be deceiving on gileras, they will spark fine on the outside of the cylinder but not on the inside aswell so a new one is reccomended, which should work, if not check yourreeds these are found under the carb inlet under the 2 8mm nuts checked there not damaged, also check your inlet for tears etc.
another problem it could also be is there is a suction valve o nthe side of the inlet make sure this is connected as its usually unnoticed but will cause the biek not to start, also check the earth from the frame as this can cause problems. good luck,
good luck again
JJ
April 2009