Harley-Davidson Maintenance: Changing the Fork Oil

When was the last time you changed the oil in your forks? The answer to this question is probably "never," "I don't even remember," or something along those lines.
This is usually the case; the truth is, the forks don't give us too many problems on Custom models, since these bikes aren't typically ridden in a sporty manner and braking is usually relatively moderate. This is why we usually don't realize that this is a part of the vehicle that also requires attention and maintenance, and that the oil inside also degrades with use and needs replacing, as it loses its lubricating properties, emulsifies (mixes with air and moisture), and damping performance is diminished.

Using the service manual
Specifically, the manual for Harley-Davidson models indicates that the oil must be replaced every 32,000 km (every 4 engine oil changes).
Well, this is precisely the task we are going to carry out, following, as always, the step-by-step instructions in the workshop book.
The first thing we have to do is put the motorcycle in a vertical position, either using a central lift or through a rear wheel stand.
After this step we will place a drainage tray under the fork we are going to work with and then we will remove the drainage screw with a screwdriver,

and oil will begin to flow out of the hole. The screw is single-use only and should not be reused. Be careful when removing it, as it is quite soft and the head can be damaged.

When the oil stops flowing, we'll get on the bike and, while pressing the front brake, we'll compress the shock absorber several times, thereby pumping out the remaining oil. Be careful to place the pan in the correct location, as this procedure causes the oil to escape under pressure.

TIP: If the oil is mixed with air bubbles or has a light brown color, the fork seals may need replacing.
Once the oil stops draining, we have finished draining. We clean the bar well and reinstall a new screw with its washer, tightening it to 2 Nm.

We fill with new oil
Once we have the fork ready we have to insert the special fork oil , for this there are 2 different methods:
-We can use the quantity indicated by the manufacturer, for which we will need a graduated measuring jug .

-The oil level can also be measured in millimeters from the edge of the dipstick with a special tool .

In both cases we must always follow the workshop manual recommendations regarding the quantity and type of oil; custom motorcycles usually use a density between 5W (light) and 20W (heavy).

Next, we need to remove the filler cap from the top of the fork tube. First, we'll use a lift to slightly raise the front wheel off the ground, thereby relieving the pressure on the suspension's internal spring.

The next step is to loosen the upper seat post screw,

This way it will be easier for us to unscrew the fork cap screw, using a specific special tool .

Be careful when unscrewing the cap, as it is under spring pressure and can fly off and dent the tank or fender.

Now we just need to fill it with the appropriate amount of liquid, using a small funnel with a rubber band, or the typical paper "cone."

If we have followed the method in the manual that indicates that we should use the extraction syringe, now would be the time.

Final checks
With the correct amount of oil in the fork, we can now retighten the top cap to a torque of 60 Nm, after which we will retighten the top triple clamp bolt to 45 Nm.
We have to repeat exactly the same procedure with the other bar, and now we can lower the bike and test it gently on the road so that the new oil recirculates.
With these simple steps, you'll see that you've rejuvenated your motorcycle's dynamic performance.

Frank Burguera

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