Pablo Azorin

I'm having some troubles to keep the rpms stable between 5200 and 6200 rpms in my Polini Thor 200 Evo. I tried replacing the Walbro carb for a FreshBreeze Bing carb, but nothing changed. With the the engine running at 5000 rpms, when I add a slightly more throttle nothing happens. Rpms still in 5000. I add more throttle and nothing, it does still in 5000. And then I add a bit more, and it suddenly goes up to 6200-6300 rpms. The same on the opposite way. After take-off, I climb at around 6500 rpms. When I want to cruise, I reduce the throttle just a little and rpms drop to 5000. It's almost impossible to keep it somewhere in between 5200 and 6200 rpms, and I need that rpms range to cruise. Is this a common problem on this engine? What can I do to resolve this issue? I was changing about replacing the reed valve for the new version that Polini launched by Sept 2014. Not sure if any of you already did it.

I'm having some troubles to keep the rpms stable between 5200 and 6200 rpms in my Polini Thor 200 Evo. I tried replacing the Walbro carb for a FreshBreeze Bing carb, but nothing changed. The engine works properly in the whole rpms range except from 5200 to 6200. For instance: with the the engine running at 5000 rpms, when I add a slightly more throttle nothing happens. I add more throttle and nothing. And then I add a bit more, and it suddenly goes to 6200-6300 rpms. The same on the opposite way. After take-off, I climb at around 6500 rpms. When I want to cruise, I reduce the throttle just a little and rpms drop to 5000. It's almost impossible to keep it somewhere in between 5200 and 6200 rpms. Is this a common problem on this engine? What can I do to resolve this issue?