Primary Drive Housings & Covers
About Primary Drive Housings & Covers
The primary housing encloses the primary chain or belt and the clutch, and on the V-twin models in these listings it is made of an inner and an outer cover. Riders shop here for a cracked or leaking cover, a new inspection cover for appearance, mounting hardware for an inner primary, or parts for restoring an older Big Twin.
The inner primary mounts to the engine and transmission, with mounting kits and lock tabs that hold it in place. The outer primary cover is the visible one, sold in finishes such as chrome and black. Inspection covers are the small covers that open to check the chain and the clutch adjustment, sold smooth, finned or with a flame design. Parts are listed by model and year range, such as Softail years and '36-'54 and '55-'64 Big Twin. Fit new gaskets and O-rings when a cover comes off, and use the primary fluid your manual specifies.
Brands here include Colony, Jims, Drag Specialties, Pro-One Perf.Mfg. and Paughco. Pick your machine in the Ride Finder at the top of the page. For what lives inside the housing see Primary Drive Belts & Chains and Primary Drive Kits, and for other drive parts see Drive Belt Pulleys & Tensioners. All are part of Final & Primary Drive Parts & Kits.
FAQs on primary drive housings and covers
What does a primary inspection cover do?
An inspection cover is a small removable cover in the primary housing. It lets you check the primary chain and the clutch adjustment without taking off the whole outer cover. Fit a new gasket or O-ring each time, and tighten the screws evenly.
What is the difference between an inner and outer primary cover?
The inner primary mounts to the engine and transmission and carries the primary drive parts. The outer primary cover bolts over it and seals the housing, and it is the one you see. Each is specific to the model range.
Do I need new gaskets when I take off a primary cover?
Yes, fit new gaskets and any O-rings. Old ones are compressed and often leak when reused. Clean the mating surfaces, tighten the bolts in the order and to the torque in your manual, then check for leaks after warm-up.
What fluid goes in the primary housing?
The type and amount depend on the model and are listed in your service manual. Some primaries use dedicated primary oil and others use engine oil, so check the manual for your model rather than guessing.
My primary cover is leaking. What should I check?
Check the gasket or O-ring, the cover bolts and the seals where shafts come through, and look for a cracked cover. Clean the area and see where fluid reappears. If the leak comes from a seal inside, the housing needs opening.
