I believe older Le Mans have that identical rear drive transmission; including the Daytona RS? The Quota 1100ES that I looked at yesterday had a breather tube running from the "B" filler cap. The filler cap was modified to include a lipped nipple onto which a rubber hose was connected and running around the frame, held by plastic straps, and opened to the ground. Clearly an oil breather; Why would you need this? the rear drive is filled up until oil comes out of "A". Is there