Apr 24, 2014. #3. When it comes to the transmission of a Sportster, I stick with a quart of HD Formula+. As for the crank, you can review the opinions of others. My school of thought is this. It's an air cooled engine. It has to lube and cool at the same time. So, change it regular and change it with something good. And you need a refill for it. Alternatively, dry represents taking the forks to bits and cleaning them dry from inside to outside. You can see that dry forks require 0.5-1.0 oz—more than wet forks. Harley’s 49mm fork oil capacity is more than 24 fl. ounces. Also, Harley’s 41mm fork oil capacity is 11.8 ounces. dNXRjm.