The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Adrian on August 16, 2012, 01:08:34 AM
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Hi again - anyone able to advise me about my front fork "problem please. I have - as far as I know - completely standard front forks that have never been modified internally in any way - I have read a lot - especially Smow bum's advice - about dismantling them for servicing but basically the advice is "don't" if they work or give them to an expert in R65 forks.
Well - as I'm restoring the bike - they are off the frame of cousre and seperate. I am in the process of just cleaning them out by emptying them out and then refilling with fresh oil - bouncing them a lot by hand - leavihg them overnight - emptying them pit again - refill - bounce and so on until all the black stuff - not too much atthis stage - stops coming out. So far so good.
The "problem" I have is that one of the legs - when bouncing - sounds like its "bubbling" or air is being forced around witht the oil while the other leg is not making this noise. I assume that I have some sort of seal - or broken seal - problem inside. I'm happy to pay to have them properly dismantled and rebuilt by my local Airhead guy cos I would like to put new progressive springs in.
So does it sound like I have an internal problem guys??? Many thanks for any advice .... Adrian
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I don't understand the concern about stripping the forks as it's easy enough and the only real way of cleaning the internal bits properly. On top of that there is a rebound bumper bush which will need replacement as it perishes and is probably the source of the black stuff.
What year are the forks and did they function properly and quietly before the bike was stripped down ? If very early forks then some other mods are advisable.
As for the progressive springs unless you are above average weight then I wouldn't at least until you have tried the stock ones. Replacing the springs at any future time is very easy and doesn't involve removing the forks from the bike or stripping them down.
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Okay thanks Barry - my bike is 1984 - twin rear shock. I would be happy to take the forks apart if it really is an easy task. I had thought that it was a simple matter to do but there seems to be warnings about the danger of damaging them upon reassemble. I thought that the blasck stuff was a washer or bush or something.
Do you know if anyone has put up on the forum a breakdown - possibly with piks - of doing the job themselves? I seem to remeber seeing somethijng on here a while ago.
Thanks for the advice - I'll certainly go back and research it again - Adrian ......
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Like Barry said, the forks are easily disassembled .
If you don't run into any issues with seized fasteners, it's about 30 minutes to take them apart .
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Okay thanks Bob - I originally thought it was a simple task from reading my Haynes manual - then I thought I'd read on Snowbum's site that it was better left to pros - then somewhere else I read that it was possible to damage the internals upon reassemnbly. Perhaps they are refering to earlier fork assemblies - thanks for the confirmation both of you. I'm too ill to do much work at any one time and I don't have much money so I try to do as much myself to keep costs down. Adrian .......
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84 forks should have all the mods already.
The only potential for damage on reassembly is to the damper piston rings and some care is needed as available replacements are inferior to the originals. No big deal.
There are several previous threads. Don't know about pictures though. There is an exploded view in Haynes which is accurate enough. This is one of those jobs that's harder to think about than to actually do. Dive in when you are ready and shout if you need any help. I've had them apart so many times I can do it in my sleep.
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lol lol okay thanks barry I guess I am over thinking it - as usual - I'll be in touch for sure if i have problems thanks - Adrian ........
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Sue did a write up on that job a long time ago. It should be on the forum, probably in the first 10 pages. I did one too, but I think it was lost with an old forum version, or something like that. Just make sure you follow R65/R45 instructions, as the other airheads differ in many details.
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You *may* need a looong extension for your socket wrench when it comes to removing and later tightening the large Allen bolts on the bottom end of the sliders/fork lowers. This bolt is what holds the whole inside of the fork and damper assembly in place - but the bolt and damper internals can rotate in place instead of tightening (or loosening) that Allen bolt unless you can hold it from the other end - which I accomplish with a couple extensions, or something like ~ 14 inch socket wrench extension inserted down from the top of the fork tube end.
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Okay - thanks Ed and nhmaf - I haven't been able to get the search box to take me to any posts that have strip down write - ups so maybe Sue might read this and guide me to it. All advice is gratefully recieved - Adrian ...........
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1. Remove the instrument crash pad lower cover - 2 screws at the sides. Unscrew the ignition switch locking ring and remove the plastic switch surround. Pull out the indicator repeater lamp holders from underneath the crash pad. Look under the crash pad and prise up 2 locating spring clips. Carefully lift the crash pad off taking care not to stress it unduly which has caused many of them to split. The handle bar throttle assembly may need to be rotated a little out of the way if the lower Euro bars are fitted - 4mm Allen screw
2. Remove the clip on plastic covers from the top of the stanchions.
3. The top plugs are held in the stanchions by a hidden wire C clip. Using an 8mm Allen key in the filler plug press down hard on the top plug approx. 25mm against the fork spring pressure to expose the C clip. Remove the C clip from it's groove by pushing it done on one side with a small screw driver to tip it vertical. You can then fish it out. The top plug will now pop out under spring pressure. Top plug removal is easiest with a 2nd pair of hands but with ingenuity can be done solo.
When this operation has been done with standard springs you will then understand that it could be much more difficult with stronger springs or pre-load spacers fitted. Therefore if intending to fit stronger springs or pre-load spacers be sure it's because you really need them and not just because "it's the the thing to do".
4. Remove the front Wheel/mudguard and brake caliper. Tie up the caliper to relieve stress on the hose.
5. Drain the fork oil.
6. Remove the fork springs from the top of the stanchions
7. The lower fork legs are held on to the end of the damper rod by a large 10mm Allen screw which is visible once the front axle is removed. Undo the Allen screw while holding the damper rod still using a 13mm socket on a long extension inserted through the top of the stanchion. With the screw and crush washer removed the lower fork leg will drop off the bottom of the stanchion. Note there is a tapered top hat damper rod seat/hydraulic bump stop in the bottom of the fork leg.
8. The damper valve assembly is secured in the bottom of the stanchion by a large strong circlip. Using circlip pliers remove the circlip and the shim/valve body/valve washer/ perforated plate/topping out bush/damper rod and piston will come out in that order. Clean and lay everything out in correct order for reassembly keeping each fork leg components separate. The only parts likely to need replacement will be the Fork seals (if not recently replaced), topping out bush and crush washers for the oil drain screws and large damper rod Allen screws. Also possibly the O rings on the top plugs if required.
Note: Removal of the damper valve assembly and damper rod can be done with the stanchions still secured in the yokes although it will involve lying on the garage floor unless you have a lift. This helps to retain good fork alignment if you already had it. Removal and replacement of the large circlip is certainly easier with the stanchions removed but removing and replacing the stanchions while retaining good alignment may not be so easy.
Notes on re-assembly
Space the damper rod piston ring gaps 120 deg apart and compress the rings carefully if inserting the damper rod into the bottom of the stanchion. Alternatively insert the damper rod through the top of the stanchion and take advantage of the tapered section below the C clip groove to compress the rings.
Use only very moderate torque when tightening the small fork oil drain plugs. The threads strip easily.
Torque the large lower Allen screw using a clean crush washer to 22 - 29 lbft. There is a potential for an oil leak here if the crush washer is not new or in very good condition.
Refill with slightly more than the 190cc of fork oil recommended for a normal drain/refill and ensure the level above the top of the damper rod is in the range 15 - 35mm. The level chosen will influence fork compliance and the extent of fork dive to some degree.
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Hi and thank you Barry - thats great info - I'll copy and Paste it to a word doc to go over carefully much apprecciated mate - Adrian ......
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I just removed the fork lowers to replace the seals, but after reassembly/check i noticed that while on the center stand, if i compress the front forks, and rock the bike back, the forks make a significant "CLUNK" upon full extension (front lifting).
Does this indicate missing/damaged damper bumpers? The clunk seems to come from both front forks...
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There's a thick rubber 'washer' that is supposed to act as a cushion when the forks go to full extension .
The washer is the black 'goo' that you'll find inside the lower fork tube when you disassemble it .
Sounds like yours has disintegrated !!!
Quite normal .
The current OEM replacement part is a red rubber washer, don't know if it will stand up better than the original or not .
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i cant seem to find the part... anyone know the part number / description?
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Here's a link to RealOEM, disregard the cost of the parts, I don't think they are current, but it gives you a part number .
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=31_0297&hg=31&fg=10
It's item #24 .
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Excellent - thanks Bob - I see they ahave greta expanded parts pictures too - very usefulas I have the bike in totally strip down - Adrian ......
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Does this indicate missing/damaged damper bumpers? The clunk seems to come from both front forks...
Hopefully it is just a missing topping out bumper bush but that is the last resort when the forks hit full extension and the bush on it's own will not always prevent a clunk.
Before the damper piston hits the bumper, rebound damping should increase noticeably over the last bit of travel as the fork approaches full extension. When the rebound damping orifice which is positioned 25mm below the damper piston falls below the damper valve washer the volume of fork oil below the damper piston has no where to go except to leak past the washer. This provides a hydraulic bump stop effect and slows the fork over the last 25mm of travel.
If you stroke the forks by hand with the springs out this increase in rebound damping over the last 25mm of extension should be very obvious. If you can't feel it then either the fork oil level is low or the oil is too thin or there is too much leakage past the valve washer.
You should also be able to detect this increase in rebound damping with the springs in place but the wheel and mudguard would have to be off to stroke one fork leg at a time.
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Barry, that was a great "How to...." Thanks for writing it up. I did mine 10 years ago and it's not exactly fresh in my memory.
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Hi again - I just re - read you instructions barry and they seem very clear thanks - as I have my forks off the bike now - the whole bike is now in bits - do you (or anyone) have an easy way to hold the stanchions while I compress the top plug to remove the circlip???
I have all thats necessary to do the rest of your instructions no probs - thansk for you help again - Adrian ......
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I bore a hole in a piece of lumber (1 inches 25 mm), cut the piece of wood and put the tube of the fork in between the pieces of wood and tighten it in a vise, then push down on the plug to expose the circlip .
I have a second piece of wood, bore a 1.5 inch 37 mm diameter hole in it, cut it and place the lower tube of the fork in it and tighten in a vise .
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Okay Bob just so i undestand what you describe - I need two vises - one above the other - to hold the wooden blocks around the stanchion - at the same time - I'm sorry mate I can't quite picture what it is you're describing - if this is correct then I don't have this facilty and it would be prohibitive to go out and buy the stuff.
How long should the blocks of wood be - how wide - how thick -how much wood should there be between the circumferenc odf the drilled holes and the edge of the wood ???
Sorry for so many questions mate - Adsrian .....
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No, I only use one vise, I put the upper fork tube in the vise first, so I can remove the circlip and top plug and get the springs out .
Then I use the larger wood blocks and put the lower fork tube in the vise, to get the damper assembly out and get the rest of the fork internal parts out .
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Hi Bob - I understand - now I can get on wiht the work - many thnks for your advice mate - Adrian .........
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I did that part of the job before I took the front tire off, so had to get up on the pegs and push the plug down.
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:D Hmm Ed - might have been worth a picture ;)
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:D Hmm Ed - might have been worth a picture ;)
It would have been, but all three hands were occupied doing the job. The scary thing is, I was by myself!
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Well Ed - lol lol - who ever said that bikers were part of the [smiley=mad.gif] normal gene pool :D