Nothing goes as planned...

[georgesgiralt]

Hi Lads,
I had a plan and an agenda today.
This morning the day started with the washing of the R65 to clean all this oil the engine has got from various leaks.
Then I planned to change the fork seal on the right leg which was leaking, then progressing from front to rear, fix the steering bearing pre-load, then the leak at the distribution cover, then the push rods, left side first then right.
Things stopped at the fork.
I put the bike back on the road in 2012 , early April. So at that time I dismantled the forks, removed the goo the rubber stop had left inside then put new seals, rubber stop, SAE5 oil and go riding. 6 month later I changed the fork oil discovering that the stop rubber has disintegrated in very small cubic parts and very brittle. So opened the fork to change the failed white rubber stop for the orange the BMW dealer provided. I did not touch the seals at that time. I surely did something wrong on the right hand tube because it started leaking  a very little then and, of course, more and more. So today was it's day.
When I opened the drain plug, with the oil came small red coloured rubber parts... I dismantled the fork just to find that the rubber stop has failed in very small bits, this time still supple but failed anyway. As I did not ride more than 5000 km since the previous dismantling, I wonder if the fork oil (Bel Ray SAE 5) is the culprit or if I missed a point here ?
This bike is becoming like a chopper : 1 hour flight, ten hour shop maintenance...
What do you think ?
Is there something I should know or am I supposed to go to the Marabout to have a disenchanting prayer done ?  

[Bob_Roller]

Usually that rubber washer isn't getting 'used' until the fork extends all the way, not overly common in my riding .

I vaguely remember you saying in a posting awile ago about the fork springs and I think spacers that were on top of the fork springs to tighten up the forks due to the full fairing you had on the bike .

I wonder if the springs may be the cause of your fork issues .

I don't think that Bel Ray oil is in any way causing the washers to come apart .

Do the fork tubes have any pits or high spots from being hit by road debris and causing 'burrs' on the fork tube that may be cutting or damaging the fork seals ?

[Barry]

Georges,

The topping out bush should be sandwiched between the underside of the damper piston and the perforated valve plate. Is that the location you have installed the bush ?  Tell me you didn't install it between the spring and the piston. That's the only place I can imagine it getting chewed up in such a short time.

If it's in the correct location the bush effectively gets struck by the piston when the forks top out but there should be nothing sharp that would cause damage.

If the forks were topping out viloently I'd expect you would hear a severe clunk.  Were there any noises ?
 

[georgesgiralt]

Hi guys,
Unless I'm deaf, no big noises. As the rubber is totally destroyed, no means to know if I put it in the wrong place last time I changed it.
I was, too, not convinced the oil has destroyed the rubber in such short time. And I am pretty certain that the Bel Ray oil was not used before. So the previous rubber was destroyed by another oil... What are the odds ? Two bad and dangerous oil out there ?  :-? I don't think so.
Last time I dismantled the fork, I measured the springs and I was glad to find they're still are the nominal length. Of course I removed the spacer when the fairing was removed.
The more I think about it, the more I think either I've assembled the whole thing wrongly, or that something is cutting the rubber stop. So tomorrow, I'll check for burrs, metal proud on tubes and things like that.
I wonder if I have the correct set of parts on the fork. So I'll buy from #19 to #24 on the fiche and replace my 30+ years old parts with brand new one.
This time triple checking on the factory manual the correct stacking and procedure. And I'll see...
Still these damn leaks to address.... And not so much time ! Grrrr.
Thanks for your advice !

P.S. Do you know how one remove the ring holder ? There is goo and small debris I can't reach at it's base and I'm unable to unscrew it.

[Rob Valdez 79 R65]

what year is the bike?

[marcmax]

I know the last time I rebuilt my forks the BMW mechanic is go to for advice and parts ( I trust his advice ) told me to use 15w fork oil. He was trained at the factory and has raced BMW's for 30 years. I did use 15w, the ride is a little stiff (I don't mind it) and haven't had any fork issues since.

[nhmaf]

I've only about 600 miles on my forks since the rebuild in June (two other bikes have limited its outings), but no worries so far - reference to my thread in the FAQ section, if you have a 1981 or later bike.   Did you place the red/orange bushines in the position as shown in those pictures?   I cannot imagine those disintegrating so quickly..   I would definitely consider using either BMW branded or perhaps Honda branded fork oil - I have had good experiences with both, and at least that might be a factor to consider for this premature failure.  
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1371526053

[Rob Valdez 79 R65]

That's why I asked the year of the bike.  I'm pretty sure the internals changed and the pictures of my '79 fork would not do him any good.

[georgesgiralt]

She was made in April 1982.
Nhmaf, the fork looks like yours except for the bottom part which is the old design (only one part and no spring).
As you've done, I'll change the exact same parts.
I hope I'll find something different on the other leg, and maybe explain why the right leg act funny.

[Barry]

The topping out bush is not shown in nhmaf's pictures. The white plastic thing to the right of the perforated valve plate is the valve washer. The topping out bush should be to the left of the valve plate as shown below.

Georges,

I'm thinking your damper components look like the picture and the diagram. The topping out bush is #24

Think about why we have the topping out bush at all. It's there to cushion the blow when the forks top out. Without it there would be metal to metal contact and the shock loading would eventually shear something off.  

Just about every other motorcycle fork including the otherwise identical R80st has a topping out spring in place of the bush which serves the same purpose.

[saintell]

I think 5W oil is too light for a road bike and would lead to bottoming out more frequently especially with fairing,15W is better,start with normal quantity and you can adjust ride feel as needed by adding or taking out a little as needed,use a hypo syringe with clear plastic tubing,fill forks to spec level and mark the clear tube then to remove some put a higher mark on the tube simply lower into each leg and suck up ,no need to do anything else but to keep a record ,cheers Nev

[georgesgiralt]

So, this morning, I cleaned everything and prepared the order to the dealer.
The more I think about it, the more I think I was wrong when reassembling the whole fork. I've found in the garbage one old #24 rubber ring. It has circular marks from the perforated washer on one side and concentric marks on the other side (maybe from the top of the damper rod). Alas I can't reuse it, it is split in two parts... So next week will be on the Honda.  

But, I still wonder, if the assembly was wrong, how did I reassemble the whole lot and still had it looking good ?

If I understand it correctly, the first piece to put on the rod is the rubber red washer, then the perforated washer, then the white plastic washer then the big support part and, last, the conical part used to centre the rod on the tube.  So the above picture miss something ?


Nhmaf, where did you get the P/N for the rings ? RealOem shows them for the big displacement engines. Did they fit the R65 fork ?

As per the oil, my  bike does not have the fairing any more. I removed it in 2012 (it was in not so good shape and I thought that at around 170 000 km I could ease her old days by removing it). I tried 10W oil and it was a little too thick (for the bad roads I have around my house) and did not ease the back pain I suffer ... The local Guru said to use 5W (and sold me the BelRay, BTW) and I was satisfied by this thickness. Maybe I could try 7.5W if I can find some.  

I measured the free length of the spring. It is at 500 ~ 502 mm depending how I measure it. So good to go.

Thanks for your help.

[Barry]

If I understand it correctly, the first piece to put on the rod is the rubber red washer, then the perforated washer, then the white plastic washer then the big support part and, last, the conical part used to centre the rod on the tube.So the above picture miss something ?  

If the damper rod and piston are already pushed up inside the stanchion bore. The assembly sequence is #24 topping out bush, 23 valve plate, #22 valve washer, #21 damper valve body, #20 shim (optional and available in various thickness),  #19 circlip that secures the damper valve assembly in the bottom of the stanchion.

#18 is the full compression hydraulic bump stop and it just drops in the bottom of the fork leg.

Oil viscosities are all over the place and quoting viscosity at 100 Deg C is meaningless. To make a choice you really have to look at the viscosity at 40 Deg C. I use 5W Castrol synthetic and consider it OK but marginally too thick (28CSt at 40 Deg C) Other 5W's like Motul (18 CSt) I found too thin.  When you find something you like use it's viscosity at 40 C to find something comparable of a different make.

15W oil tends to be in the high 40's or 50 CSt and I imagine would make the ride very firm. Definitely not for me and not what BMW intended.

[nhmaf]

Barry - if you look at the pics I put on PAGE 2 of my earlier thread - you will see the damper assembly put together with new parts in the proper order.   George- the later pics include pictures of the BMW parts in their factory packaging, and shows the part numbers, including those of the piston wiper rings.   I got the rings from going to the local dealer, who has a man in their parts department who is VERY knowledgable in airhead parts.   He triple checked that these were the proper parts, and I think that he was correct.

My suggestion for using BMW or honda fork oil isn't so much a matter of viscosity, but chemical nature-thinking perhaps there is something about the Belray oil you tried which is not compatible with the red plastic bumpers.    It isn't likely the case, but do you want to be doing the job all over a third time - unless you determine that there was an assembly error that caused it.

At least with the old style one piece damper valve, you are not trying to apply 75 pounds of force to compress that spring so that you can install the bottom circlip!    

[Barry]

Barry - if you look at the pics I put on PAGE 2 of my earlier thread - you will see the damper assembly put together with new parts in the proper order.  

OK I see it now.

Georges set up will be the same except he has the earlier single part valve body.