What fuel, plug combo are you running. I had a macstar that I recently sold with one of my buggies. I to had a problem at first. I was using the suggested plug with bad results. Switched to a OS A5 and it helped. The needle settings I used. HSN 3 3/4 turns from closed, MSN flush with carb body, LSN flush with linkage collar, idle screw 1.5mm opening. Running O'Donnell 30% race blend. After that I was able to run 240-270 F with good acceleration and top end. Hope this helps. You can atleast use these needle settings as a starting point.