garrod

I have a 1993 Gas Gas 250 that has developed a problem, It`s quite hard to start and when it does it idles ok but if I open the throttle it sounds like it`s hunting and will not rev up then sounds like it runs out of fuel and stalls! I have a spare carb that has just been re done and it does the same with that! The spark looks ok and now I`m lost as to what else it could be! Help anyone? Many thanks.