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Fork oil

ba-heed

New member
Hello all round, I would like to change my fork oil on my 1980 R100RT. After checking the specs I have looked for Aeroshell 4 but can only buy a case, so Plan B what else shall I use? all advice gratefully received, Heed
 

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Bel-Ray

I have used Bel-Ray - used to be the fork oil standard.

Can be had at virtually any mc dealer.

Change often!
 
fork oil

I have the same year, though different looking forks. A&S Motorsports recommended BMW Motorrand Grade 7.5.
SnowBum is an amazing source of information. Unfortunately I don't always have the band width to follow his writings. Wish I did.
 
Brand is pretty much irrelevant (as it is with nearly all lubricants). 7.5W seems to be most popular for avg weight folks. 5w if you're slight, 10w if you're robust.
 
Unfortunately, 5w by one brand won't feel like the same 5w by another brand. This is something that a person has to try out and see what works. Once you found what you like, stick with it.
 
I replace the PJ1 7.5 wt fork oil in my '78 with Mercon V automatic transmission fluid. The forks feel about the same to me. I made the switch because some extra ATF was available and I have another lower fork to swap out for a dual brake conversion. Also, my '77 Clymers manual describes using hydraulic fluid in the forks and ATF is hydraulic fluid. The viscosity looked about right from the Mercon V specifications and the forks feel OK to me. Fork feel is somewhat subjective so YMMV.
 
Many have used AFT with no issues, I have and added about an ounce of seal swell to the mix to help with the fork seals.

You can adjust the weight from 5- 10 to suit the type of riding you do. The 7.5 is a base line and for the weight and type of bike that should be fine. The type of valving in the fork really determines what fork weight oil works best ( in the manufactures eyes ) but that doesn't apply if you fall outside the base line ( type & weight of riding etc ). Some want a little softer front end and some want a firmer front end. There are many manufacturers that make fork oil and any of the popular brands will work fine. The bike won't know the difference, as long as its fork oil.

Don't get too hung up on brand names. If its fork oil it will work.
 
Spectro or BelRay usually for me, at present 5w Spectro in my ST but I discovered that Kubota SuperUDT hydraulic fluid seems to give the right feel in the R100 rig.
Experiment with a few different things to find what feels right to you. . . .including different brands, varying the weight AND the volume (a bit).
 
After rebuilding my forks, I experimented a bit with Bel Ray and Maxima (and maybe PJ1?). I also played around with the weights (5, 7, and 10wt). Through my very unscientific process, I finally settled on Maxima 7 wt fork fluid. The Maxima fork fluid does seem to reduce stiction over the other oils I tried. The 7 wt seems to match my springs (Progressive Suspension) nicely. I liked the Bel Ray 5 wt also, but it seemed like the forks were a little underdamped for the springs I had installed- it might have worked with the stock springs, though.

http://www.maximausa.com/shopping/index.php?main_page=product_info&products_id=44
 
I've experimented with PJ1 and Bel Ray. Went back to the standard 7.5 BMW oil, it seemed to work best for me. At about $7 a quart it is probably cheaper than the others! Oh, by the way, the back of the bottle says it was formulated by Spectro. Works for me, I'm a happy camper, errr, I mean rider.
 
video?

Does anyone know if there is a video on changing for oil on a /6 or /7. Not one doing a rebuild, just a fork oil change.
 
On a slash six isn't it just a matter of taking off the cap and using the hex key/ socket trick? If I remember right when you loosen the lock nut you can push the hex doodad back up breaking the seal and the oil drains out.
 
I've had good luck on my F800 running Mobil 1 ATF. Feels great but the stuff I took out was two different colors and probably two different weights. When I first got the bike it blew a fork seal and the dealer only replaced the fluid in one leg when I took it in to get it fixed for free.

On a slash six isn't it just a matter of taking off the cap and using the hex key/ socket trick? If I remember right when you loosen the lock nut you can push the hex doodad back up breaking the seal and the oil drains out.


If it's a damper rod fork the tail end of a spark plug socket should fit it perfectly into the top of the damper rod allowing you to remove the allen bolt in the bottom easily.
 
Your results might vary but years ago I put the Aero Shell in my R80 and my seals leaked shortly after, requiring replacement. Buy some BMW 7.5 from your favorite dealer. It works.
 
On my /7, I hold a socket with a pair of vise grips...this let's me go up the middle of the socket with the allen wrench to hold the damper rod from turning. Loosen the nut and remove it. I then keep the allen wrench in the end of the damper rod and shove it up into the slider...helps if the front end is off the ground. When finished draining, wiggle the allen key to get the damper rod to fall back into the hole. Repeat the process with the socket-vise grips to tighten up. Pretty much all forks are the same up to the late 1980s...Type I forks.
 
If I remember correctly, To drain the /6 forks, don't know about other models;

first place on center stand front wheel off the ground, full extension of telescopic forks
Second remove the rubber bottom (dust) caps to expose the 13mm nuts.
Third using a box wrench (13mm hex) loosen/remove the nut while holding the internal hexagon (4mm key) from moving
Fourth remove the upper "fill" caps with the pin spanner to vent. Don't remove the receptacles that these thread into (large Hex) as you will release the fork springs. Use care as sometimes the two will be stuck & come out together. The fork springs being released unexpectedly may cause you physical harm if you are in line with the fork tubes.

At this point I diverge by removing the lower plugs (using the big "dog bone" ring wrench)

The oil and other contents will drain easily and completely.

The removal of the large bottom cap allows for more complete drainage including debris in the chamber. The condition of the "bumper" that insets into the large cap may be inspected for deterioration & replaced as needed. As these bumpers disintegrate the loosened "bits" contaminate the fork oil (mine did for sure) and they also fail to perform their "bumper" function . The replacement bumper is of an improved material and was white, the old was black.

Having the replacement lower big copper washers on hand along with two new bumpers, washers for the top caps the lower "rubber dust caps" and new wave washers for the 13mm nut would be wise.
 
For me, I pretty much follow the routine of Amiles above except:

Having the bike on the center stand and the nuts removed off of the bottom of the fork, by holding the Allen wrench, and then set the nuts and wavy washers aside. I DO NOT remove the bottom cap assembly with the associated hardware. Instead, as the owners manual advises to do, have a couple of pans ready under the forks to catch the fluid that is now going to FLOW........PULL DOWN on the bottom of the forks. The forks will move perhaps an inch or so in a downward movement and the fluid will gush out into the pan or onto the floor. Let it drain.

Now, you can push up on the bottom of the forks and seat the threaded rod back through the bottom of the fork or one can just roll it off the center stand and let gravity do the work. Reinstall the wavy washers with the nuts and NO one does not need to super torque those nuts. Put the bike back up on the center stand and refill with the required fluid and amount. God bless......Dennis
 
On my /7, I hold a socket with a pair of vise grips...this let's me go up the middle of the socket with the allen wrench to hold the damper rod from turning. Loosen the nut and remove it. I then keep the allen wrench in the end of the damper rod and shove it up into the slider...helps if the front end is off the ground. When finished draining, wiggle the allen key to get the damper rod to fall back into the hole. Repeat the process with the socket-vise grips to tighten up. Pretty much all forks are the same up to the late 1980s...Type I forks.

This is the method I use as well. Works great! It's certainly easy to ID the 13mm socket in my cabinet, what with the plier marks. It seems like I saw a post or article where someone ground two flats on a socket for an open end wrench... can't remember where I saw it though.
 
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