The first half of your post with your 75% and 100% throttle and how engine ran makes me think it's too lean on the main needle but not enough so that is totally cuts out, so try richening the main needle 1/4 turn and see how that works out. The last 1/2 of your post confused me and you said something like the engine wasn't hot enough to make your spit bubble off of the engine's head, so from that it could be too rich and doesn't have any heat in the cylinder. If main needle is too lean and at full throttle is cuts out like someone is turning engine off and on or it slows down a good amount then main is too lean, If it slows down but is burbbly and rough sounding and good amount of smoke out of the pipe then main is too rich.