I'm traveling right now and thus am operating from memory only but my first thought is you're not getting quite enough fuel at this point. Jon (Carbking) mentioned that's not the proper float but it seemed to work ok and when I looked at this I didn't have a spare float of the proper type. The drop level is slightly less important than the level from airhorn to the float, but if the float level distance between the float and airhorn became less than 7/16 or 15/32" it might be out of range. Let's see if the other Jon chimes in...
