This is what Keith at BME writes in the engine manual. The high octane fuel should not be used. May cause engine to run hot.


FUEL:

We recommend standard 87 octane unleaded gasoline for your BME (Chevron and Texaco seem to work very well). Higher-octane fuel will not generate more power and may cause the engine to run slower and overheat. Try what is recommended first!

Note: The use of alcohol is to be avoided and will void the warranty. Alcohol-based fuels are highly corrosive to the carburetor and internal engine parts, and the carburetor must be modified in order to pass the proper amount of fuel to the engine – otherwise severe overheating will occur and the engine will be damaged.