Would the bike automatically switch to the open loop mode and run rich?

 

YEah, it won't run right and it will through a code.

 

Will run in open-loop mode and throw a code. Will probably run fine, though, although lean like before.

 

I believe the primary purpose is to adapt to the fuel. The closed loop will correct for other sources of variation but the fuel is the biggest variable. Gasohol has oxygen and gasoline doesn't. So that alters the mass of fuel you need given a mass of air for a complete burn since you may or may not be getting oxygen from the fuel in addition to the air.