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?