A thermal isolator between engine and carb makes a HUGE difference.


Next step: getting the solenoid system set up, to get the engine to run as lean as possible throughout the RPM range, for two reasons: in this engine, the negative influence of unburnt fuel on the properties of oil is HUGE (and strangely enough, running temperatures drop significantly with a lean mixture), but the 2nd reason is that at part throttle, the lack of fuel metering makes the engine wasteful to the extreme: