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F-Twins Tech - F800GS Renewing Fork Oil

drneo66

Well-known member
The articles, posts and comments in this tech section are posted by individual members and reflect their personal thoughts and experiences with repairing, maintaining, and generally working on motorcycles. This information may require specific knowledge and skills, may or may not be correct or current to model.

The authors of information found here and the BMW MOA take no responsibility for ensuring the accuracy of any information (including procedures, techniques, parts numbers, torque values, tool usage, etc.), or further for any damage of any kind or injuries incurred or caused by anyone following the instructions or information found here.

It is the duty of the individual to either assume the liability himself for responsibly using the information found here, or to take the bike or accessory to a Dealer or other qualified professional service.


Please ensure you dispose of your used chemicals, oils and fuels in an environmentally responsible manner. Most Auto Parts stores and service stations will accept used oil and lubricants, tires and batteries, please check for your local availability. Here's a link where you can look up a place to dispose of your used fluids (oil, coolant, brake fluid, etc.) - http://earth911.com/

This article, text and photos are Copyright of the individual authors and the BMW MOA, any copying or redistributing is permitted only by prior written authorization.

PLEASE PRINT AND READ ALL THE INSTRUCTIONS BEFORE BEGINNING!

Final note: When in doubt, take your motorcycle to a reputable dealer.

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Renewing the fork oil on your 2013 or later BMW F800GS

Changing the oil in your forks is just as important as any other fluid in your motorcycle. As you ride your bike, your fork oil slowly gets dirtier and loses it's proper oil viscosity. This can result in premature wear and tear on the forks as well as contribute a rougher ride. It's much easier to spend an hour or two of your time along with $15 of fork oil, than have to replace parts in your forks (new forks will run you $2400 at the time of writing).


Note 1: The specific bike shown is a 2013 F800GS using WP forks, older bikes have a similar process, but use a different style of forks (Marzocchi).
Note 2: The tools and materials used are by personal choice and are not due to any affiliation with any brand.


Fluids Required:
SAE 7.5 wt Fork Oil - we need about 1220 milliliters or 41 ounces (1.3 quarts)

Tools Required:
- 24mm socket (preferably 6-sided)
- T25 star (Torx) bit
- T30 star (Torx) bit
- T45 star (Torx) bit
- E12 external star (External Torx) socket
- 17mm socket
- 13mm open end wrench
- Ratchet(s) that fit the above
- Torque wrench
- Suitable way to raise the front wheel and keep the bike steady
- Container to catch the used oil
- Your least favorite shirt/rag
 
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We will need to remove the front fender, brakes, and front wheel so we can remove the fork legs.

Start by removing the front fender. On each side of the fender, there are plastic pieces that hold the brake lines in the proper place. These are held in by plastic snaps, so gently pop each plastic piece out.


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Remove the three T25 star (Torx) screws on both sides of the forks, as indicated by the green arrows.

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Using your E12 external star (External Torx) socket, remove both bolts on each of the brake calipers, as indicated by the arrows

Note: the wheel and fender are still attached to the bike in this photo

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Using your T25 star (Torx) bit, remove the brake line retainer on the throttle-side fork. This can be gently opened more to clear the fork leg for removal.

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Remove both calipers from the fork legs and brake discs. Make sure to tie them up out of the way or place them on a suitable holding device to relieve any pressure on the brake lines.

Take a moment and clean the bottom, chrome portions of the fork tubes. Because we are going to slide the fork tubes all the way down to the axle holder, any dirt/bugs could effect the dust and oil seals. Five minutes of cleaning may prevent premature fork seal death, so it's worth it to make sure the sliders are clean.


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We are going to work on one fork leg at a time so we don't mix up parts between each fork leg.

Using your T45 star (Torx) bit, slacken the top clamping bolts (A and B as indicated by the green arrows)

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Using your 24mm socket, partially unscrew the top cap of the fork. Using a paper towel between your socket and the top cap will reduce the risk of marring the top cap.

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We will now remove the fork leg from the bike. Using your T45, slacken the lower clamp bolts, as indicated by the green arrows. Make sure you have one hand holding on to the fork leg, as the fork could slip out of the triple tree.

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We can now remove the top cover from the fork. Use your 24mm socket to unscrew the top cover all the way.

Then, using your 13mm open end wrench, and your 24mm socket, loosen the lock nut located on the underside of the top cover (indicated by the green arrow). You may need to spin the spring around a little bit to get a good grip on the lock nut with your wrench.

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Here is the top cap off. Note that there are two spacers that are in the recess of the top cover; most of the time they seem to stay in the cover itself.

I don't believe the spring is wound progressively, but out of habit, I mark the top of the spring with a twist tie so I remember the spring's orientation.

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We can now extract the spring from the fork leg. The spring will be coated in fork oil, so you may want to lay down a protective cover over your garage floor to ease cleanup.

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We can now dump out the old fork oil into our suitable container. The plastic piston rod will extend as you tip the fork upside down, so be careful that you don't damage anything. We want to push in and draw out that plastic piston rod several times to expel all of the fork oil, so this may process may take some time.

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Once all the fork oil is drained out, we are ready to refill. The 2013 and newer F800GS's WP forks call for an air gap of 61 mm when the fork is fully compressed and the plastic inner damper rod is full. To measure this air gap, you can purchase the proper BMW tool from your dealer (BMW Tool number: 31 6 551), use an aftermarket tool such as Motion Pro Fork Oil tool, or the newly-released Thom Rieck's multipurpose, eco-friendly, and dolphin-safe amazingly wonderful Fork Oil Poker Tool (Patent-pending 2019) available at only the most exclusive of motorcycle dealers for $24.95 , which is also known as a chop stick with a red pen mark at 61mm.

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Slowly draw the plastic inner dampener all the way up and push it all the way down several times to move the fork oil into the damper. You will notice that, as the damper rod is filled it becomes more difficult to move the damper rod.

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Once the bubbles in the fork oil have settled and you have made sure the damper rod is all the way at the bottom of the fork and the fork is fully compressed, slowly fill the fork with the remaining oil until you achieve a 61mm air gap.

If you using the chopstick (DrNeo's wonder tool :brad), align the mark we made on the edge of the chopstick with the edge of the fork tube, and fill the fork with fluid until the fluid just touches the bottom of the chopstick. Take your time, as it's not easy to remove excess fluid.

Note: this picture shows the chopstick partially removed

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Congrats - you've replaced you fork oil! We can now install the top cover to the fork and begin replacing the fork onto the bike.

First, screw the locking nut on the plastic piston dampener all the way down. Next, pull the piston rod all the way up, so it's fully extended. Then, carefully slide the fork spring over the dampener rod. Finally, screw the top cover back onto the plastic dampener rod. This may take take a little bit of coordination as the dampener rod has a tendency to want to slowly retract down.


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