Fork oil change.

[Captain Black]

On a roll........just changes the front fork oil and replaced with Shell advance 5W fork oil.
Both stantions had about 400ml in, but what was interesting was the right fork oil was fairly clear still, apart from some black oil at first which i assume is whats settled at the base of the stantion. The left fork however, the oil was as black as the coals of hell, any reason for that? No leaks and both had appx 400 ml in when i drained them. Just curious, as not sure how long fork oil is good for? My guess is it gets over looked most of the time in services.....perhaps??

 

[GEOFFREY DEACON]

forks,

BM reccommend 10 k oil changes, but this should depend on your usage etc,
One leg oil being more dirty is possible that one fork seal may have been replaced in its past or your dust seal or gaiter is weak enough to pass dirt through..

or may have had RTA damage

 

[Steptoe]

5w fork oil

 

[Rob Farmer]

5w fork oil

10W is standard in the Para's

 

[Captain Black]

10W is standard in the Para's

Just my luck.....i had a litre of 5w and 10w, so plumped for the 5, it does'nt state anything in the hand book. I'll use the 10w when i do the 100PD.....

 

[(RIP) Proff]

2/4 W on my 90s's
MIL-H-5606E
"AKA >> "BMW red fork oil".


IIRC it was same oil as fitted in Aircraft suspension and brakes in the 40's/50's...



Look what I found
Due to how specified, and lack of stiction fighters and other characteristics, you are MUCH better off with a REAL fork oil....especially a full synthetic fork oil. For fork oils and suspension fluids, the various manufacturer's do not agree on measuring viscosity; and sometimes don't do more than give some approximate SAE grade value. Viscosity measurements and temperatures is vastly more cut and dried for engine and gear oils, not so for these oils. Because of this, I highly recommend you stay with ONE manufacturer if playing with viscosity grades. Except for some GS models, all the old BMW's needed a very thin oil, roughly SAE 4 (that military oil, as above), so do not willy-nilly change the viscosity grade to higher....as only in the instance of VERY heavy loads (rider and passenger weights and luggage) is an oil heavier than an actual 7.5 weight of any benefit. NEVER higher than SAE10, for the non-GS models (some GS models specifying use of different oil, say 10 and 15, in left and right fork legs). I have other things to say about the GS in the HINTS section near the end of this long article. A high viscosity INDEX is a good thing. There is an article on this website on actual values for fork oils...here is, again, that link (and it has other oil information too):

http://bmwmotorcycletech.info/viscosity.htm


I remember this wiper ring problem as well>>
WARNING!
***The early forks contain what BMW calls "wiper rings" buried inside the mechanism. You can call them piston rings. I HIGHLY RECOMMEND that you do NOT replace them. New rings from BMW are NOT properly made, do NOT fit correctly, give too much friction, and OLD ones generally will work BETTER than new ones, since they slide easier. Any minor extra INTERNAL oil leakage due to wear is usually MINIMAL

 

[Eng]

Fork Oil

Had this black oil issue: at the bottom of the slider is a rubber bumper that sometimes gets soft and deteriorates, remove slider and replace or if you change the oil a couple of times after a 1000 miles or so it will eventually come clean. Some folks with dirty internals put diesel in and "scragg" (correct technical term) the forks up and down to clean. Drain overnight and hey presto clean internals. 221 cc is the correct ammount of oil for most airheads. "That" old military oil is OM-15, red hydraulic fluid, better spec than most bike fork oils and readily available. My aircraft has 72 gallons of the stuff in the system, so 221 cc is readily available.

 

[(RIP) Proff]

Had this black oil issue: at the bottom of the slider is a rubber bumper that sometimes gets soft and deteriorates, remove slider and replace or if you change the oil a couple of times after a 1000 miles or so it will eventually come clean. Some folks with dirty internals put diesel in and "scragg" (correct technical term) the forks up and down to clean. Drain overnight and hey presto clean internals. 221 cc is the correct ammount of oil for most airheads. "That" old military oil is OM-15, red hydraulic fluid, better spec than most bike fork oils and readily available. My aircraft has 72 gallons of the stuff in the system, so 221 cc is readily available.

Why don't you bring a gallon or two to Airhead WeeKend ???
I've run out of the good stuff 2 years ago

 

[Damien]

Mil-H-5606 is still used in modern aircraft undercarriage struts!

 

[Beemerboff]

You will notice a difference with the best full synth HVI suspension fluid you can find.

Less stiction, consistent damping over the temperature range and stays in grade twice as long too.

Maxima or Belray work well for me ,the 5 wt Belray works fine in the old style forks on my GS and /7 and the 7.5 Maxima in the GS with HPN inserts.

Lasts twice as long, so doesnt end up costing any more in the long run.

 

[Box’a’bits]

There might be a simpler explanation for the different coloured oils I think. My first fork oil change on my '91 GS also encountered different colours. The two fork legs may have used different oil weights. On your Para, the compresssion & rebound functions are separated between the two fork legs.

Spectro does a clear 5w, blue 10w, & rasberry red 15w.

I'm fairly sure the previous owner used 10w left leg & 5w in the right.

I run 12.5w (a 50/50 mix of 15w & 10w) in the left leg, and 10w in the right. The fork legs also take 410cc & 440cc respectively for a fork oil change.

 

[(RIP) maverick]

Had this black oil issue: at the bottom of the slider is a rubber bumper that sometimes gets soft and deteriorates, remove slider and replace or if you change the oil a couple of times after a 1000 miles or so it will eventually come clean. Some folks with dirty internals put diesel in and "scragg" (correct technical term) the forks up and down to clean. Drain overnight and hey presto clean internals. 221 cc is the correct ammount of oil for most airheads. "That" old military oil is OM-15, red hydraulic fluid, better spec than most bike fork oils and readily available. My aircraft has 72 gallons of the stuff in the system, so 221 cc is readily available.

Is this the same stuff as the OM-15 fluidhttp://www.silmid.com/Products/Lubricants/Aeroshell-Lubricants/Aeroshell-Hydraulic-Fluids/ASF41005LT.aspx

 

[Sunny Jim]

Bought a set of Wilbers progressive springs for the '91 GS when last at Wunderlich and a bottle of Wilbers 7.5 - and intend fitting shortly but this thread seems to be telling me I needed a higher rating - any advice welcome chaps.

Oh yes, can someone confirm the fluid per fork is as seen when sat on the 'bike and looking forward pse

 

[GEOFFREY DEACON]

Use ATF, automatic transmission fluid,(5-10w oil), Buy it from a car dealer, "cheaper",,
It used to be fitted to all Police B*W Bikes,
i have tried 15w and 20 w but it made the bikes harsh on the rebound, but It did not wobble about after a good bump or two..