The derby is the cover on the left side of the bike where the primary oil goes. It'ts called a derby cover,
Harley Davidson "Derby Cover"A "Derby Cover" is basically a dust cover. It's on the left side of your bike and covers the business end of your clutch. It's the larger cover with (usually) 4-6 screws holding it in place. However my '85 Sportster has no screws in the "Derby Cover". Instead there's a two inch (2") screw-cap in the center of my "Derby Cover" with a large closed slot in the center. That's it! there are no other screws holding it in place.
The Iberian derby i think.
The Bowler and the Derby is the same hat. The British call the hat a Bowler. The Americans call the hat a Derby.
remove the derby cover from the primary. Fill until it tries to run out. Replace derby cover.
remove the derby ( round ) cover from the primary. fill til it tries to run out. replace derby cover.
remove the derby (round) cover from the primary. fill until the fluid tries to run out. replace the derby cover.
the large round cover on the rear of the primary three screws over the clutch
The "Derby" is the large dome-shaped cover on the primary. The primary is on the left side of the engine. Be VERY careful when removing the derby fasteners. The screws on the derby are very prone to stripping. Insure that any tool is inserted all the way to the bottom of the slot before placing any force on the fastener.
The cover over the points / timing set plate on the right side of the bike.
Remove the derby ( round ) cover from the primary. Fill until the oil tries to run out. Replace the derby cover. Most of us run the same oil in the primary as in the engine.
remove the derby ( round) cover and fill until it tries to run out of the derby hole.