Scorpion Derby Covers / '99-'23 Big Twins

Barnett's billet derby cover with a quarter inch polycarbonate window, so the clutch is visible without opening the primary.

Most derby covers hide the one part of the drivetrain worth looking at. Barnett CNC machines the outer body from billet aluminum and sets a 0.25 inch clear polycarbonate window into it, held by an O-ring gasket that seals the joint against primary fluid. Polycarbonate is the material choice that matters here: it resists the scratching and yellowing that turn a cheap acrylic window cloudy within a season, so the view stays a feature rather than becoming a defect.

Features of the Barnett Scorpion Derby Cover

• Quarter inch thick clear polycarbonate window over the clutch
• Scratch and discoloration resistant, so the window stays clear
• Outer cover precision CNC machined from billet aluminum
• O-ring gasket seats the window and seals it against primary fluid
• Derby cover gasket included
• Chrome or Stealth black anodized finish
• Made in the U.S.A.

Scorpion Derby Cover Fitment

Three application groups, each in chrome or black. Choose the one that matches your bike.

• '99-'06 Harley-Davidson Twin Cam
• '07-'18 Harley-Davidson big twin, except '18 FLSB, '16-'18 dressers and '15 FLHTCUL and FLHTKL
• '16-'23 Harley-Davidson dressers and FL Trike, plus '15 FLHTCUL and FLHTKL

⚠️ VERIFY which group your bike falls into before ordering. The exceptions above are not typos: Harley-Davidson changed the derby opening on the dresser models mid range, and the '15 FLHTCUL and FLHTKL take the later cover despite the year.

Common Questions About the Scorpion Derby Cover

Will it leak?
Not if it is installed correctly. The window is sealed to the cover with an O-ring, and the derby gasket that seals the cover to the primary is in the box. Torque the derby screws evenly and to spec.

Can I actually see anything through it?
Yes, with the bike running you can watch the clutch basket turn and the pressure plate lift. It is also the fastest way to spot a primary fluid level problem or a leaking pushrod seal.

Does it work with a lock-up clutch?
Barnett recommends pairing it with one of their lock-up clutches, and the window is the easiest way to confirm a lock-up is behaving as it should.