► Forks--clonks, gaiters and leaks

[mark2jag]

forking clonks, or is it the other way round...

Anyone with the 800GS getting any clonking noises on bumpy ground/potholes? I'm sure it's pretty normal but perhaps someone else here can confirm it. I can reproduce it with the bike stationary and pumping the forks. It also gets a tad louder if on partial lock so i'm guessing it's just the fork internals.

I have absolutely not a scooby whats causing it but mine does the same too, but only when stationary. Dealers absolutely no bleedin help, err so far, so im just gonna have to ask different ones, or do what you are doing and ask on here.
I do hope theres someone out there with more mechanical knowledge than me, but to be honest it wouldnt be hard.......onyack

 

[Wookie]

Just an update on the outcome on our Clonking forks. Both of our bikes were making the clonking noise riding over 1inch deep pot holes (Bikes 250 miles 1 weeek old).
Got a mate to help out and we checked the headstock play properly. Found that both bikes had excessive play in the headstock, much more than id ever seen before on a road bike thats done 10k miles....

Had a chat to the dealer we bought from and he advised us to contact the BMW emergency warranty people as we were both concerned with riding the bikes the 50miles to the closest dealer.
Phoned the Warranty people at 12pm on sunday. The mechanic was at our door by 1pm. Unfortunately he wasnt able to sort the problem there and then but arranged for the bikes to be collected 8am monday morning for delivering to bristol. After a few false starts with returning (seems recovery companies dont like trasnporting 2 bikes at the same time ) both bikes were fixed and returned by 6pm tuesday .

Moral of the story... Clonking forks are NOT internal problems. If your bike is making a noise check your head stock bearings thoroughly and contact the offical BMW warranty people for assistance.

PS Best way to check head stock bearing involves 3 people.
1st person sits on the pillion seat with the bike on the centre stand. This will raise the front end of the ground.
2nd person place fingers around bottom of headstock where it meets the bottom yoke.
3rd person grabs bottoms of fork tubes and tries to move forks back and forth. You will get some natural flex in the forks but lose headstock bearings will be felt as more of a clonk/jar.
Whilst doing this the 2nd person will be able to confirm the amount of play around the headstock/bottom yoke/top yoke. There shouldnt be any play here at all.

 

[Koopz]

Rebuilding - Front Forks

I have searched but found little information and as I have never rebuilt front forks is there anywhere I can find the correct info. Can anyone direct me or provide the info before I go too far and end up with a mess!

I am replacing the existing springs with Ohlins.

Do I just take the weight off, unscrew the top, lift out the old springs, put in new oil (how much?) stick the new springs in and screw the tops back on?

(can it be so simple?)

All contributions gratefully received.

S

 

[Snapperuk]

Me too!

I asked a similar question myself but didn't get any replies! I don't want to go to the expense of changing the springs if they are already progressively wound.
I've changed quite a few springs in my time and the important info needed is oil weight, quantity and air gap.

Getting the fork legs out usually goes as follows but this method is only based on machines I have worked on and not specific to the GS.

Support the front of the bike with a jack under the engine and remove the front wheel, mudguard and brake caliper. Hang this from the handlebar on string to take the weight off the brake hose.

Loosen the top fork nuts at this point as it makes it easier to unscrew them later.

Working on one leg at a time, loosen top yoke pinch bolts then the bottom ones until the fork leg can slide out. You may need to spread the clamps slightly to do this.

Undo the top fork nut carefully so that the the spring does not shoot out as it may be under tension. There may also be a spacer tube on top of the spring.

Having withdrawn the spring, drain the oil by either removing the drain screw or turning the leg upside down. Leave to drain, pumping it occasionally to remove as much oil as possible.

Supporting the leg vertically, (Usually compressed and it's useful to have a Workmate here) refill with the correct amount of recommended fork oil. This can be a measured amount or a specified air gap to the top of the fork tube. (Which is a more accurate method as it takes into account any remaining oil present.) Install the new spring as per manufacturers instruction.

Reinstallation is simply a reversal of the above process.

Please remember I have not tried to do this yet on my F650GS and there may be problems that I am not aware of, but I hope it gives you a general idea.

 

[alimey4u2]

Have a chat with Ohlins or Harris-Performance

 

[Greggers]

Are you talking about RSU on 650 or USD on the 800?

RSUs are fairly straightforward, I got my TY20 legs down to 30 minutes to do get the wheel out, legs off, do both seals and reinstall everything. The only sticky point you might get is removing the bolt which secures the damper rod - use a windy-gun or fabricate a long rod to hold the nut inside the fork tube.. withdraw the tube, hook out the seals, install new ones and reverse assembly.

USDs are a little more complex - I've done a couple of sets of R1 forks, and needed to make a special tool to allow me to release the damper rod which is at the top of the fork... As BMW see fit to create a master cylinder reservoir which requires a special tool to open it, it's entirely possible that there's some obscure component that has a unique fitting that only the BMW approved hexadecimal thrust widget will remove... I'll check the manual and will get back to you...

G

 

[Koopz]

USDs are a little more complex - I've done a couple of sets of R1 forks, and needed to make a special tool to allow me to release the damper rod which is at the top of the fork... As BMW see fit to create a master cylinder reservoir which requires a special tool to open it, it's entirely possible that there's some obscure component that has a unique fitting that only the BMW approved hexadecimal thrust widget will remove... I'll check the manual and will get back to you...



That will the difficult one then!

I have located an exploded diagram showing the top which indicates that there is just a cap then the spring. As the bike has only 1200 miles on it can I change the spring and keep the oil, unless this is easy to do.

May give it a go today.......................

 

[Snapperuk]

USDs are a little more complex - I've done a couple of sets of R1 forks, and needed to make a special tool to allow me to release the damper rod which is at the top of the fork... As BMW see fit to create a master cylinder reservoir which requires a special tool to open it, it's entirely possible that there's some obscure component that has a unique fitting that only the BMW approved hexadecimal thrust widget will remove... I'll check the manual and will get back to you...



That will the difficult one then!

I have located an exploded diagram showing the top which indicates that there is just a cap then the spring. As the bike has only 1200 miles on it can I change the spring and keep the oil, unless this is easy to do.

May give it a go today.......................

So have you done it and how did you get on?

 

[dholaday]

See this thread.

http://www.advrider.com/forums/showthread.php?t=456787

 

[OZRIDER]

The stock OEM springs are linear. Ohlins have a heavier weight set of springs but Hyperpro do a progressive spring set. Also YSS (which is a hyperpro spring re-branded and cheaper) is also progressive.

 

[Koopz]

So have you done it and how did you get on?

Oh yes, I was sent an extract from the workshop manual from a member (thanks G).

Essentially this suggests that you remove the forks but as mine ar evirtually new I did not need to replace the oil so I came up with the idea of supporting the bike on the centre stand and jack on the plate and do as indicated on the Adv site.

All very easy and was completed in about 40 minutes

I now have ohlins front and rear and these are significantly different to the OE items, i'll let you know if they are worth it when I am back in October!

S

 

[jarax]

Hi, i am rebuilding front forks wit hyperpro progressive springs. Does anybody know the torque setings for all the nuts/bolts holding front forks? I definitelly have to remove them (crashed in accident) and change them for new ones...

scanned page form manual will help...

thanks

 

[Greggers]

Koopz..

So - what did you do to the rear end, and how much did all the bits cost..?

Greg

 

[Koopz]

Re the rear end I put an ohlins shock as sold by both TT and Motor Works, the same unit being about £450 cheaper at the latter. The front inserts from MW being about £75 I think.

The unit has the hydraulic pre load adjuster made for the 800 and again is very simple to install and took about half an hour to complete.

I have the pre load near max as I will be fully loaded with the panniers and bits and as a result it runs about 5cm higher than OE so a bit of a stretch to flat foot.


S

 

[Koopz]

Jarax,

Post me an e mail address and I can pass on the info that I was sent the details go through the full rebuild with settings.

By the way, going through Prague and spending a day I think on 14/15th June with rest of RTW crew.

S

 

[chrisjk]

How much do your forks

protrude above the triple clamp?

I started to get antsy about my suspension not performing as I would wish and in considering what to do I looked at the maintenance CD about the fork set up, I realised that the forks were not set as per the manual which calls for 7.8mm of protrusion above the clamp - indeed there is a ring on the fork tube which I had never noticed because mine were too low - practically flush with the clamp.

Out of interest I started looking at all the photos I could see that showed the 800 cockpit in sufficient detail as to see the fork position. A majority appear to have been set like mine were originally and I wonder why? I reckon enough people used to moan about the steering being too slow and the bike too tall for this to have been an owner's choice but rather how they got the bikes.

 

[lawe]

The forks are not set up according to the service manual at the factory. That's a strange fact.

I lowered mine to the marking and like it that way: A little bit quicker.

/Lars

 

[everywherevirtually]

Bouncy Forks are fork oil change and service

I had a service last week and one of the items on the list was a fork oil change.

Over the course of this week I've noticed how terrible the suspension is. Even the smallest bump in the road and the bike is bouncing off them

I'm no expert on suspension but something doesn't feel right. I'm expecting it to bed in as it's full of new fork oil?

I also notice that when I lift the bike up off the side stand it pauses for a moment then drops as the forks take the load of the bike. It drops by about a centimetre. Not dissimilar to when you sit on a swivel chair. For a moment it takes your weight then it drops a little bit.

I also noticed that the top of the forks are different. Back in March the piece on top was flush with the clamps. Today they are 0.5cm above the the clamp???

Does this change anything? The geometry perhaps and secondly... is this correct?

I've included some photos to demonstrate.

Has anyone had a similar experience? Or is more knowledgeable on the subject.

Many thanks

Jon

 

[Ducksbane]

F800 Forks

I noticed on another site that the forks were probably designed to be lower in the triple clamps .... it's s easy to change them (5 minutes) and it does steer better. It also lowers the bike a little. I didn't notice any reduction in stability.

The one negative I did notice was that it made the forks proclivity to bounce of small bumps a bit worse. I wish BMW had thrown a bit more money at the suspension, after all the 2009 Husqvarna's (owned by BMW) use the same brand of suspension at each end, but you can tell they spent a bit more on it!

Anyway, I have some hyperpro progressive springs waiting for me next week, so I am hoping it will make it just a bit better.

 

[Greggers]

Jon ..

It might be that the fresh oil is just doing its job better than the cheap shite they probably used to fill the forks with from the factory... If your dealer used a different brand of oil with perhaps a different grade, then the damping characteristics of the fork will change... It's also possible that too much oil in the forks can affect the springing (more oil = less air to compress = higher internal pressure..) which might affect the way the bike feels.
As far as the mounting in the yokes is concerned - I read somewhere that they are supposed to mounted with some of the stanchion through the yoke - best check the bike-porn to see for sure. It might be that your mechanic actually has RTFM and done the job by the book. Dropping the yokes by that small amount will change the geometry, but by such a small amount that you'll probably not notice a change.

Greg