DIY Tech: How to change the fork oil in most Harley-Davidsons
As stated in the engine oil and filter change article in issue 380, nowadays almost every motorcycle owner knows the importance of changing their engine’s oil and filter at the manufacturer’s recommended intervals. This is done to keep the engine from wearing out prematurely since the molecules in even the best oil break down after many hours of operation and can then no longer properly protect the engine’s internal moving parts. However, when it comes to their motorcycle’s front forks, many owners completely forget that the oil in their bike’s front end also needs to be changed regularly. In fact, some owners don’t even realize there’s oil in their bike’s front end! Thankfully, unlike when performing engine, transmission, and primary system oil changes, which are easier to do with the motorcycle on a bike lift, the front fork oil is replaced with the bike on the ground. And, like the oil in your bike’s transmission and primary system, the perfect time to change your front end oil is on a rainy Saturday or Sunday.
In most cases, Harley-Davidson recommends changing the fork oil annually or every 10,000 miles. And, as it is with the transmission and primary system, different year and model bikes require a different amount or type of fork oil. The owner’s manual for the 1993 Evo Softail FL model we’re working on in this article specifies a wet quantity of 11.5 ounces of H-D Type E fork oil. Many year and model bikes, like our 1993 Softail FL, have two fork oil quantities listed in their owner’s manuals and service manuals: A wet quantity and a dry quantity. If you’re just draining out the old oil and then adding fresh oil, you use the wet quantity of oil. However, if you disassemble the front end and wipe all the old oil from the internal parts, once the front forks are reassembled you must use the dry quantity. For our 1993 Evo Softail FL, the dry quantity is 12.5 ounces. Be sure to check your service manual for what type and quantity of oil your bike requires.
Again, as it is with the transmission and primary system, though the fork oil should be changed at or near the mileage intervals recommended in the H-D service manual, if you push the job off for a while as you wait for that rainy day, it’s no big deal. However, some owners take this too far and push the job off for thousands of miles. Not good! Even when there’s enough oil in there, it doesn’t mean the oil can still protect the moving parts of the components involved or smooth out your ride as it should. If the oil quantity in each fork leg is less than it should be, the negatives are increased. But how could there be less oil in the fork legs if you’ve never had any traces of oil under the front end? Though the drain screws on the sliders and the slider (fork) tube caps on the fork tubes are not leaking, what about the fork tube seals in the sliders? A fork seal can be leaking oil without leaving any drops of oil on the ground. Have you ever wiped a slight oil stain off the fork tube just about the slider? While the quantity is slight, it all adds up. After all, each entire fork assembly only holds about 12 ounces of oil. If you’ve had to wipe dirt off the fork tubes just above the sliders, it means the seal is letting enough oil pass by it that road dirt is sticking to the oil coated fork tube.
That said, check out the accompanying 15 photos and captions to see how easy it is to do this required bit of motorcycle maintenance in your own garage without jacking up the bike.
• Drain pan
• Clean rags
• Blanket or towel
• Measuring cup
• Small funnel
•#2 Phillips screwdriver
• 3/8″ wrench
• 1-3/8″ wrench
• Torque wrench (ft-lbs.)