mine runs better when B is covered with a plug. it's a vacuum port used to go to the big evap. can on my CA legal '85. there is a vacuum controlled valve in the can that is activated when the motor runs. it effects the mixture when you don't have anything connected to it and will drive you crazy.
Originally Posted by m2h
Mine have petrol hose attached and fed down to a securing loop on the right side behind the brake lever. Probably better than leaving them as is in your pik.