The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Swimd01 on August 27, 2015, 04:17:11 PM
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Does anyone have a good write-up / pictures for how to do a full maintenance on the front forks?
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There is a thread about this, two postings down from this one, ' Fork disassembly for dual shock R65'S 'can't open it at work, so I don't know anything about it's content .
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[movedhere] R65 Technical FAQ/Procedures [move by] Justin B..
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A disaster, or what? Whilst removing my front wheel I noticed the L fork leg had dropped a centimeter or so, making ot difficult to locate the axle. The leg would not compress, so I removed the front fender attatchments. The leg would not compress. Instead it came out completely from the upper tube, without any bottom stop being evident. What the heck is going on here and is it remediable. This is a new fork leg, installed for the previous owner by a third party BMW engineer?
Help much appreciated, please....
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Hello Andrew,
Not exactly a disaster but could be...
The tube still on the bike has a threaded bottom end. Normally, when this tube is on the fork leg, there is a screw holding it in the leg; If you look on the "removed" one, you'll see the hole in it for the screw and if you look on the other fork leg, you'll see the screw.
IMHO, either the mechanic did not torque the screw at all or torqued it too much and ruptured it.
So if you put everything back properly, it will not be a disaster ;-)
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It's not clear from the picture where the damper rod #25 is. Had the bottom screw #17 come out I'd expect to see the damper rod still located in the fork stanchion. Unless of course you have removed it
Other possibilities are the circlip #19 holding the damper valve body in the stanchion has come out or the damper valve piston (top bit of #25) has come off the top of the damper rod. It could have unscrewed or it's not completely unknown for them to shear off. Unless you saw an oil leak prior to the leg coming off I'd say one of these latter possibilities has occurred.
If you haven't removed the damper rod and you don't have all parts 19 to 24 on the floor then I say it's the damper rod piston that's become detached.
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Hi, and thanks for responding. No leak prior to event. Nothing yet removed. The fork leg came off the stanchion exposing the spring. I have not investigated further. Also, the first sign of the problem was total lack of compressibilityof L fork leg as I tried to align axle; it hit a hard, metallic stop internally. I rode the bike for 9 event free miles 2 days before..
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Your first step might be to remove the large circlip in the bottom of the stanchion (if it's still there). The damper valve assembly should then fall out and you can see if the damper piston is still inside. If it is it might be canted over and jammed which would explain your symptoms.
Also look down inside the fork leg and tell us if you see the damper rod which is a thick walled metal tube 16mm in diameter and threaded at the top. If you can see those threads then the damper piston has become detached and as in above paragraph, may be jammed inside the stanchion.
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Thanks, Barry. I'll check as suggested. I'll report findings...
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Well, No circlip in evidence at the bottom of the stanchion. Confirm the allen bolt is present in the bottom of the leg. I can't figure out what would stop the leg dropping off the stanchion in normal use!
Photos herewith...
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The damper rod (25 in photo) if it still exists, will still be firmly bolted to the sliding part of the fork that is now laying on the ground.
Looks to me that most likely the circlip at the base of the fork tube was not installed correctly and as that is all that keeps the innards "in" you have the situation pictured.
To the OP, unless there has been some serious, even bizarre, skulduggery you have an easily fixed problem.
Shine a torch down the fork leg that fell off and I suspect you will see the 13mm top of the damper rod. You will need a socket and extension on this and a suitable allen key at the base of the leg to undo the bolt that goes into the bottom of the damper rod. If you have an air wrench - use it on the bolt as it gives you better chance of undoing the bolt rather than the top of the damper rod.
If the top comes off the damper rod you will need to clean the threads with brake cleaner and then use Loctite green and put it back. Once the loctite sets up you can have another go at the real target - the bolt at the bottom.
When you get it all out, take photos and post them here.
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In above
Pic. 1 looking down the fork leg
Pic. 2 bottom of the stanchion..look no circlip
Pic. 3 lookin up into the top of the stanchion..
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Thanks, Tony. Your diagnosis seems to check out so far...
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Sorry I missed the second photo sequence.
100% either circlip not seated correctly on assembly or simply forgotten.
Get the bolt in the bottom of the slider out, inspect all parts for damage (unlikely) and put it all back together with a correctly installed circlip and all will be well.
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Well at least you had the simplest cause of failure. When the big circlip goes back in be sure to get it the right way around. They are usual stamped out so have a slightly rounded edge on one side and a sharp square edge on the other. You want the sharp edge facing outwards so it locates nice and securely in the groove.
You haven't mentioned the year of this bike so the damper valve assembly might not be exactly as the diagram above which is the earlier type. Later ones had a shorter sprung valve body.
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Following on from Barry's post, some assemblies ended up a bit short (or the bottom of the fork leg was machined too deeply) and the maker of the forks fitted shims - if the shims are not present then the damper body (21 in the photo) can move up and down. This causes a really annoying noise and may (and I stress the word may) lead to premature failure of the circlip.
Check to see if your No.21 has any movement after fitting the circlip - if so you need to obtain shims. My memory tells me that the shims from some other BMW model fit.
BMW had two goes at this - the first attempt was to fit shims, which in my opinion is the correct way to go, their second attempt was to use a variety of circlip called a "seager" clip which has a number of raised right angled components that act to "pre-tension" No.21 so it can't move.
I think firstly that the seager clip approach is mickey mouse and secondly that they are a bastard to fit, in fact i suspect that many R65s that had them now do not because the mechanic rebuilding the forks couldn't fit them, or they flew across the workshop, never to be seen again, and were replaced by an un-shimmed circlip.
I confess that the garden next to where I work on my bikes has a seager clip somewhere within it.
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My own forks had 20 thou end play in the damper body and no shim so I made one to fit. In the diagram above the shim is #20 and they are still shown in the parts fiche in various thicknesses so may be available from BMW. The story I heard about the seager circlip was it was introduced to save the assembly line workers the trouble of selecting the correct shim size. The valve body was later reduced in length and a short spring fitted above it to take up any play.
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..the thick plotens..
I managed successfully to remove the 10mm damper rod screw with an air impacter. Sadly, the internals reveal a broken buffer, but no sign of any additional shims, or valve washer.
The pesky circlip was there, however, languishing in a pile of rust stained gloop.
So, I'm in the process of ringing around Motorworks/Bins, and Sherlock. No joy. Even trying BMW Park Lane....!
Any further suggestions from out there??
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I've placed an order with AScycles CA for the dead buffer and valve washer. Also a shim and new circlipfrom Motorworks.
I strongly suspect a less than thorough job from the previous repairer, especially as all this started yesterday, when I aimed to remedy the direction of rotation of the front wheel.
Thanks, all, for your information...
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It's very common for the bumper bush to break up or dissolve into mush and it's the No1 thing to replace when forks are overhauled. Your BMW man can't have been familiar with R65 forks or he would have replaced it.
That looks to be the later type of circlip with spring tabs to take up any play without using shims. Have you ordered a plain circlip and shim to replace it ?
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When I overhauled my forks recently the red buffers were mush too but unfortunately not available from Motorworks or Motobins and none in Europe according to BMW dealers.
Not discontinued though which I find amazing as really the only part that deteriorates so can’t be reused.
Would be interested to know if they actually can get hold of them.
Had to use an alternative.
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All cleaned up. Bush comments above noted. The end float is 10 thou. I shall see what turns up from Motorworkscirclip and shimwise.
Regards, all. :)
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Hello MrTall100,
BMW is said to search for a new part maker and a new material for these bumpers. So as far as I know, the part will be available again soon ... which could take months or maybe years...
Motobins and my local BMW Guru advise to use a bushing from the /5 or /6 forks. It is made from hard plastic so won't replace the bumper perfectly but... will survive the first 100 km ;D
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Hi George,
Thanks for the help, think that’s the one I used in the end. Motorworks had the brown one on back order since July 2017 so a year when I rang so I didn’t have much hope they would turn up in a week :'(.
We will see how this one get on.
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Current:
Velocette Venom 1957
BMW R65 1984
I am a former Venom owner - a mid 60s edition owned when I was young and impressionable in the 70s.
Naturally I spent a King's ransom on go-faster bits and pieces and generally got it as close to Thruxton specifications as I could.
It was like the girl in the poem "when she was good, she was very, very good, but when she was bad she was horrid".
Wish I had it now to ride on Sundays.....
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....so AScycles want $40 shipping to UK. But it's not in stock anyway..Start again.
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This bumper fits from Motobins. As Georges mentioned they are not as soft as the BMW originals but on the other hand they don't disintegrate. I've had them in for over 10 years.
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Many thanks, Barry. What an invaluable resource this forum is.
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I've just disassembled the right fork. Much tidier, but bumper bush disintegrated as predicted. Motobins/works parts arriving tomorrow, so rebuild and upandrunning by Friday....unless, of course I attack the L spider exhaust clamp nut to get at the sidestand Allen machine screw head to rebush same.... I feel a new topic coming on.
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Get your blow torch out !
Saying that I soaked mine for two weeks in penetrating oil only to find them not tight at all.
Good luck
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..the thick plotens..
The pesky circlip was there, however, languishing in a pile of rust stained gloop.
And it is of the "Seeger" type I mentioned as being a barsteward to fit, and that difficulty is the probable cause of your current "difficulties".
If it is undamaged I'd have a lash at fitting it properly.
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to get at the sidestand Allen machine screw head to rebush same.... I feel a new topic coming on.
Having done one recently - good luck.
Do clean out the grease passage and fit a new grease nipple.
At least the post 81 bikes have a readily obtainable bush, the 79/80 owners are on their own as it is NLA and is different to the bush used in /7 machines. Those you get to make yourself. And, if you have a set of bastardised R65 exhaust pipes mated to an R80 engine, you have to cut the bolt and use a half height nut.
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Thanks, Tony.
Back to the forks ----all reassembled, and back on the bike, with front wheel now rotating in the correct direction. lSlight niggle: the initial damping characteristics were not the same in both legs after rebuild, off the bike. I put this down to oil settling into the correct spaces?
Test ride tomorrow, and carb balancing Friday ( the side stand will have to wait).
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Slight niggle: the initial damping characteristics were not the same in both legs after rebuild, off the bike. I put this down to oil settling into the correct spaces?
They are very simple dampers, the oil should be more or less fully 'distributed' at first stroke. A difference in damping so large as for you to notice it by hand suggests that you have other gremlins in the system.
Still, if it rides OK, I would not worry too much - if I were to place a bet I'd say that a piece of disintegrated red damper is currently lodged in one of the bleed ports in the damper rod. If so it will likely deliquesce further over time and the damping rates will equalise.
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If by any chance you are feeling substantial compression damping on one leg then there is something wrong. The only damping you can easily feel by hand is rebound damping. Compression damping is so weak that it's hard to move the forks fast enough to feel much especially with the springs in.
I test damping by stroking the legs individually without the springs. You should feel rebound damping to be at least 3 times stronger than compression and you should feel rebound damping increase further over the last 1" of stroke at full extension.
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Thanks. Yes, rebound damping is more on one than the other. Compression damping not evident. Hoping for a dry day tomorrow...
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If so it will likely deliquesce further over time
Darn it Tony. You made me pull out my dictionary. I understand from the sentence what you mean but I have never seen that word and I can't just let that lie.
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Darn it Tony. You made me pull out my dictionary. I understand from the sentence what you mean but I have never seen that word and I can't just let that lie.
Sorry, but it describes so well what the red rubber bump stop does. The term is usually used by coroners to describe what (for example) a body sealed in a plastic bag with a few litres of Hydroflouric acid does.
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Sorry, but it describes so well what the red rubber bump stop does.
Tony , it was the perfect word. The fact that you could reach out and use it keeps us in awe. You guys and the Brits really have a command of the language. We in the West just fumble along in 3rf-4th place
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Successful first forks renovation ride this morning; no squeaks or rattles on a sinuous, rural route. Stopped outside Sharpness docks to do an initial pilot adjustment, followed by further balancing back home. Raining now.
As a bonus, I found both exhaust spider nuts easily removed, so side stand rebushing next job.
Many thanks to all who helped me understand and fix my forks.