If you are unsure about which size derby cover you need to fit your Harley-Davidson, don’t guess. Give me a call and we’ll get it sorted out.
I make six different sizes of Harley-Davidson derby covers – covering most bikes built since 1970:
- Milwaukee Eight Softail Models (five hole)
- Milwaukee Eight Touring Models (five hole)
- Twin Cam big twins (five hole)
- Shovelhead and Evolution big twins (three hole)
- Early model Sportsters (four hole)
- Late model Sportsters (six hole)
The only models I don’t support are the Ironhead Sportsters that don’t actually have derby covers.
To determine which Harley-Davidson derby cover size you need, follow these steps:
- If your derby cover has three holes, select “1970-1998 Big Twin (three hole)”.
- If your derby cover has four holes, select “1994-2003 Sportster (four hole)”.
- If your derby cover has six holes, select “2004-2022 Sportster (six hole)”
- If your current derby cover has five holes, there are three possibilities, and the best way to confirm the correct size is to measure your current derby cover:
- Select “Milwaukee 8 Softail (five hole – 6.4″ dia)” if you have a Milwaukee 8 engine equipped Softail model (eg, “Street Bob”, “Low Rider”, etc) from the 2019 model year or newer. This derby cover is 6.4″ in diameter.
- Select “Milwaukee 8 Touring (five hole – 7.75″ dia)” if you have a Milwaukee 8 engine equipped touring model (eg, “Road King” or “Tour Glide”) from the 2017 model year or newer. This derby cover is 7.75″ in diameter.
- Select “1999-2017 Twin Cam Big Twin (five hole – 7.25″ dia)” if you have a Twin Cam equipped bike from those years. Touring, Softail, and Dyna models all use the same size. This derby cover is 7.25″ diameter version, and was also used on the last year Evolution (1999) bikes.
Note – 2018 Softail models were a crossover year. They came equipped with the new Milwaukee 8 motor, but mostly retained the previous (Twin Cam style, 7.25″ dia) outer primary and derby cover. If you have a 2018 Softail, verify that your derby cover is 7.25″ in diameter, and select “1999-2017 Twin Cam Big Twin (five hole – 7.25″ dia”) when ordering. The exception is the 2018 FLSB Sport Glide. That one takes the newer, 6.4″ dia derby cover. If in doubt, measure!
Details of Every Derby Cover Style I Make:
NOTES:
HD really changed things up with this design. There are pockets on the back that fit into standoffs on the outer primary, and the top pocket is notched so the cover will only fit one way. In addition, there is a groove not found on any other model around the outside of the back edge.
This size is also unusual, in that it requires 10-24×1/2″ mounting bolts. Every other size uses 1/4″-20×5/8″ bolts.
NOTES:
Harley calls this one “narrow profile”. This size is used on all Milwaukee 8 equipped touring models, and also on the last year Twin Cam touring models.
At 7.75″, this design has the largest diameter of any derby cover HD has made to date. I don’t like the flat O-ring style gasket from HD. Accordingly, I supply James gaskets with my derby covers.
NOTES:
HD used this size from 1999 until 2017. Primarily found on Twin Cams, it was also used on some last-year Evos. Note that some 2016+ Twin Cam models use the 7.75″ size, rather than this one. Always measure the diameter of your current derby cover to make sure which one you need.
Your current cover may or may not have a gasket channel machined into the back, as HD made them both ways. I do not put that gasket channel in my derby covers, They require the flat style gasket (available from HD or James).
NOTES:
My life would be a lot simpler if every derby cover style was as straightforward as this classic. “Three holes and the truth.”
My guess is that HD added additional mounting bolts because these tended to warp. The high quality bronze used in my derby covers means mine don’t have that problem.
NOTES:
With four holes and the familiar lump for the clutch cable at the 7:00 position, this design is easy to identify. If your current derby cover has four holes, this is the one you need.
Unlike Big Twins, Sportster derby covers actually serve a mechanical purpose, with the spring holder ring in the inside center.
NOTES:
With six holes and a slight lump for the clutch cable at the 7:00 position, this design is easy to identify. If your current derby cover has six holes, this is the one you need.
Unlike Big Twins, Sportster derby covers actually serve a mechanical purpose, with the spring holder ring in the inside center. The spring holder on the six hole version is so deep, rather than cast it, I CNC machine it.
