Motorcycle Oil and Clutch Friction:

Q: What oil do you recommend for my primary chain case?

A: We recommend using  JASO-MA, JASO-MA2, JASO-DH/L approved oils. These oils are suitable for unit engines where the wet clutch and engine share the same oil. Do not use MB rated oil, it has too many friction modifiers and can cause clutch slippage. Reference your service manual, it will provide change schedules, viscosity, and the correct amount of oil to use. (On the back of the oil container there will be a JASO box with individual certification number). Shell Rotella, which we recommend for use in vintage British machines, has proven to a very good choice.

Automatic Transmission Fluid can be used in primary cases of machines which use separate oils for the engine, primary and gearbox. JRC clutches will operate properly with any of the ATF fluids on the market. (Ford “Type F” fluid will give a more positive clutch engagement, and is more suitable for competition riding.) IE: Triumph twins prior to 1970 utilized a timed breather and a seal on the crank. Beginning in 1970 Triumph utilized the left hand crank bearing and primary to breath crankcase gases.

Worn or damaged clutch components will also affect clutch performance, thoroughly inspect the clutch assembly during installation.

Our clutches can be used in a “Wet or Dry” application. For wet applications soak clutches for 10 to 15 minutes before installation. For moist application soak clutches for 10 to 15 minutes, wipe them off with lint free cloth before installation. For dry applications install right out of the box.



MB grade oils are classified as the lowest friction oils among motorcycle four-cycle oils. Not to be used where a JASO MA grade oil is required.