Great looking conversion. I just started running a Graupner 15/8 three blade on my 24.5 Robin with CH Ignition and am getting about 7200 RPM as well. I have a WT391 11.1mm carb on mine. What carb are you running and where did you get the carb adapter. I'm using the original adapter and bored it out as much as possible. Still less that the carb opening.