The short answer: To change Harley-Davidson* primary oil, remove the drain plug under the primary case with a 5/8-inch socket, fit a new O-ring and torque the plug to 14–21 ft-lb, replace the primary cover gasket, then refill through the cover (about one quart on a Softail) and check the level. Confirm the capacity for your model in the owner’s manual.
Periodically changing primary oil guards against chain, gear and bearing wear while helping prevent clutch slip for confident takeoffs. It’s a simple job you can do with basic tools and a little know-how. Here’s how to perform a Harley-Davidson* primary oil change.
Likewise, AMSOIL Synthetic V-Twin Primary Fluid is “over-engineered” to protect primary chaincase components. Its viscosity is like an SAE 50 motor oil. Formulating it as a straight-weight lubricant naturally offers an advantage in shear stability over multi-viscosity lubricants. This helps the fluid remain thicker, which helps it cling to the compensator without being “flung off” as easily for maximum protection.
In Harley-Davidson motorcycles, the compensator acts as a shock absorber to prevent engine vibration from affecting the transmission. Compensator wear often leads to a knocking or ticking noise. Synthetic V-Twin Primary Fluid also clings well to the chain for excellent wear protection. And its wet-clutch-compatible formulation meets JASO MA/MA2 requirements.
For this demonstration, we’re using a 2014 Harley-Davidson Softail Fat Boy Lo.
Video transcript: AMSOIL Tech Tips: Harley Davidson Motorcycle Primary Change
Welcome to Tech Tips. I’m Len Groom. Today we’re changing the primary fluid on a Harley-Davidson* motorcycle. Let’s check in with our trade show manager and in-house motorcycle enthusiast Patricia Stoll on how to do that.
Today we’re going to change the primary fluid on a Harley-Davidson Softail. This just happens to be a 2014 Fatboy Low. Before you begin this procedure, you’ll need a few items. I have this handy dandy primary funnel.
You’ll want a drain pan, a new O-ring, a five-eighths inch socket, a T27 Torque bit, your socket wrench and a torque wrench, your primary cover gasket and, of course, some AMSOIL V-Twin Primary Fluid. First you’re going to want to locate your primary drain plug, which is located right below your primary case. Next we have to remove our primary cover. You’re going to need your socket wrench and your T27 Torque bit.
So there’s five bolts, so make sure you set them somewhere safe and you don’t lose them. So now that I’ve removed all five bolts, I’m going to remove the primary cover and set it aside. Next we’re going to drain our primary fluid. You’re going to want your five-eighths inch socket and your socket wrench.
So you want to slide your drain pan into place, and I like to remove it by hand so my drain plug doesn’t fall into the primary fluid. Okay, it’s coming. Next we’re going to replace the gasket on our primary case cover. You should be able to pull the old one right out.
Get rid of that. Grab a new one and it should drop right into place. I’m going to put that in there and I’m going to set it aside now that my primary fluid has drained and put my drain plug back in. So I’ve cleaned the drain plug and installed a new o-ring.
I like to start it by hand and then snug it up with my socket wrench and my five-eighths inch socket. Now you want to take your Torque wrench and you’ll want your Torque wrench set at 14 to 21 foot-pounds of Torque. I have mine set at 16. Okay, we should be set.
Next we’re going to fill our primary with oil. I like to use my handy dandy funnel which is designed for a primary case. And I like using AMSOIL synthetic V-twin primary fluid. Remember Harley-Davidson soft tails require one quart of primary fluid.
Now that we’ve filled the primary case with fluid, double check the fluid level visually. The primary fluid should be touching the bottom of the clutch plate. Now we’re going to replace the primary cover. I’ve already installed a new gasket.
So put our cover on, get a bolt. I like to start them by hand. I’ve finished snugging up the bolts on my primary case cover. I’m going to take my Torque wrench and my T27 Torque bit and tighten them to the proper setting.
Your Torque wrench should be set at 84 to 108 inch-pounds of Torque. Remember when you tighten the bolts on your primary case to tighten them in a star pattern. Much like you would the lug nuts on a car tire. So I’ve finished torquing all the bolts on my primary case and we’re done.
That’s all there is to changing the primary fluid on a Harley-Davidson soft tail. Remember, as you change the oil on your individual bike, check your owner’s manual for capacity or go to the lookup guide at amsoil.com. Thanks for watching. We’ll see you next time.
Tools you need for a Harley-Davidson primary oil change
- Primary funnel
- Drain pan
- New O-ring
- 5/8-inch socket
- T27 torque bit
- Socket wrench
- Torque wrench
- Primary cover gasket
- AMSOIL Synthetic V-Twin Primary Fluid
- Locate the primary-fluid drain plug, which is right below the primary case.
- Next, use the socket wrench and T27 torque bit to remove the primary cover. There are five bolts; make sure you set them somewhere safe so you don’t lose them. Set the primary cover aside.
Drain the primary oil
- Slide your drain pan in place, then use the 5/8-inch socket and socket wrench to loosen the drain plug. Remove it the rest of the way by hand so it doesn’t fall into the drain pan.
- Next, replace the gasket on the primary case cover. You should be able to pull the old one right out. The new gasket should drop right into place, then set the cover aside.
- Clean the drain plug and install the new O-ring. Start it by hand and then snug it up with a socket wrench and 5/8-inch socket. Set the torque wrench to 14-21 foot-pounds of torque and tighten the plug.
Fill the primary with oil
- It helps to use a funnel designed for a primary case. Harley-Davidson Softails require one quart of primary fluid. Be sure to check your owner’s manual or the AMSOIL Product Guide for the correct primary oil capacity for your bike.
- Once you’ve filled the primary case with fluid, double check the fluid level visually. The primary fluid should touch the bottom of the clutch plate.
- Finally, replace the primary cover. After hand-tightening each bolt, use a torque wrench and T27 torque bit to tighten them to the proper setting. Your torque wrench should be set at 84-108 inch-pounds of torque. Remember to tighten them in a star pattern much like the lug nuts on a car tire.
That’s all there is to performing a Harley-Davidson primary oil change. Make sure you dispose of the used oil properly. For your specific bike, consult the owner’s manual for oil capacity and viscosity, or check out the AMSOIL Product Guide.
Check out how to change oil on a Harley-Davidson motorcycle and how to change transmission fluid on a Harley-Davidson.
This article is part of our Motorcycle Oil and Maintenance guide. See every article in the guide.
Hey John, Thanks for the information. Currently I’m using the AMSOIL Synthetic V-Twin Oil for my Harley-Davidson. It’s an amazing oil for V-twin engines; I highly recommend the oil for all Harley users.
Thank you for providing such an informative essay on engines.