Gilera purejet 50 to 50 sp engine fast idle help!!!!!!!

Hi im normally pretty good with these sort of things but i am absolutely stumped. As most of you will know i bought a gilera 50 purejet with the engine knackered so i got hold of low mielage 50 carbed engine for pennys. got it all in wired up correctly and bam wont start. changed the fuel lines and put a tap on the bottom of the the tank but ive also put a pump on it aswell. all well and good the bike fires in to life but revs to high. ive checked all the cables and adjusted the mixture to the correct settings but still no joy.I think its due to the pump but seeing as the tap is at the bottom of the tank and its lower than the carb i assume that it will need some sort of push to get to the carb?? am i wrong in doing this as it maybe chucking to much fuel down???

Just to let you know its just the engine and loom thats been changed on the purejet everything else is standard purejet issued. help please this is making me loose sleep cos its so frustrating lol