The Harley Davidson service manual is very specific about achieving correct fork oil capacity. The steps to perform this service are detailed yet simple, as Bob and Mark demonstrate in this video on how to fill fork oil on your Harley Ultra.
With the 49mm fork tube fully extended; pour, slightly more than, 24 fl. oz. of fork oil into the fork tube. Next, actuate the fork to to fill the internal dampner cartridge. Pump the fork tube until greater resistance is felt.
Use a fork tube holder, a second set of hands, or your lower tree to hold the fork tube fully extended.
*TIP* Use your lower tree to hold your fork tube when learning how to fill fork oil. Slide the tube into the lower tree so that the top of the tube is, only slightly, above the top of the lower tree. Tighten the pinch bolts. Your bottom tree is now acting as a fork holder tool. This is a good idea if you do not have a second set of hands to help, or if you do not have access to the correct tool.
Set your fluid extractor to 3.74″, or 95mm. Set the extractor flush, on the top of the fork tube. With the tube fully extended, extract the excess fluid. Now, your fluid level is set to the correct factory specifications.
You can now reassemble the fork tube. Install the progressively wound fork spring in the same direction as it was removed.
*NOTE* The tube is progressively wound. The “tighter” end should face downward, (or go in first). There are some applications where the direction of a progressively wound spring does not matter. However, that is not the case, in this service.
Next, install the washer/spacer, and the (tube) spacer. The tube will stand approx 2″ above the top of the extended fork tube. That is correct and is considered to be the preload. Prep the fork tube cap with a new o-ring and teflon paste. Then install and torque to the correct factory torque spec.
Fork oil is an integral part of your front end. Incorrect fluid level, or old/tired/dirty fluid can adversely affect the handling of your motorcycle. Correct, thorough service of this area is crucial.
You will need to change your fork oil at every factory recommended service interval. You will also replace fork oil when replacing fork seals & bushings, tubes, or any time there is a need to completely disassemble the fork assembly.