Primary cover on a Harley-Davidson big twin
Checking and maintaining the proper level of fluids in your Harley-Davidson is important. In addition to the engine and transmission, the primary case requires fluid to lubricate the primary chain and clutch plates.
You check your primary fluid level through the inspection cover, which is the oval cover in the middle of the primary cover. You’ll need a T25 Torx wrench to remove the bolts. Have a new inspection cover gasket in case you need it.
Add the fluid through the inspection cover. You can use any kind of oil — petroleum or synthetic — as long as it does not contain friction modifiers.
Closing the Inspection Cover
Replace the gasket on the inspection cover if needed. Tighten bolts finger tight; then tighten the bolts at 10 foot-pounds. Start with the top bolt and then tighten the bottom bolt. The third bolt is the right one, and the left bolt is last.