Front fork guide bushes

[Rusty Bolts]

How easy is it for a DIYer with a good understanding of engineering and maintained but limited equipment beyond a comprehensive tools kit to strip the front forks and replace the guide bushes on a 07 GS?
I have an unusual knocking noise and what seems like play between the stancion and slider. My money is on the guide bushes. The bike has done 108k miles and this noise has just started in the last couple of thousand. Checked the clamp bolts and all the other things such as telelever ball joint and bearings.
I am also resigned to removing the offending fork leg and taking it to a main dealer if required.
Any thoughts on the ease of repair?

 

[Pukmeister]

Have you checked the amount of free play on your front brake pads in the calipers. With wear and thrust, the pads become very loose and can clatter about under suspension movement giving rise to some hard knocks felt through the bars.

My GSA does this to a lesser extent, my old R1 is particularly bad for it.

I've rebuild plenty of RWU and USD forks but never needed to strip any BMW front slider tubes. Can't be too hard though as they are unsprung.

 

[Rusty Bolts]

I thought that about the pads and pins so I have changed them but no change. I know the front discs do move but this noise is coming from above the discs. The front shock is a Wilbers less than 12 months old. I have taken it off and greased the bottom rose joint. All seems good to me. If I stand on the left hand side of the bike, apply the front brake and feverishly rock the bike front and back I can see what looks like movement on the right hand leg. It looks like the slider and stancion are not moving in line with each other, almost looks like they are bending. Of course this may be an optical illusion. If there was this amount of movement I would expect to be able to grab the front fork and feel large amounts of play. It may be a case of removing the fork leg and seeing what's way. It may be the combination of clamp and top yoke are keeping things from moving too much.

 

[Pukmeister]

Sounds like a fair enough reason to strip and inspect. If in doubt it's best to be 100% sure they are in good condition.

I was inferring more towards the pads shuttling up and down slightly within the caliper rather than worn pins etc, obviously they need a bit of clearance but with wear and mileage it can get worse and worse:

If I just bounce my front suspension it's quiet, but if I pull/hold the front brake lever and bounce it then it clunks up and down as the pads grip the disks and then rattle in the calipers.

I believe the front 'forks' on the GS still have oil in them for lubrication but no springs. Perhaps a fork oil change might help?

 

[(RIP) trickytree]

Got some Rockster/R1100S fork bottoms in bits at the momment. I removed the top bush by making a slide hammer with some threaded rod, nuts, washers and a large socket, worked fine. No idea how to get the bottom bush out however.....although I doubt I'm going to bother as even dry and with a badly scored top bush the stanchion slides into the slider with a gentle air cushioned push and there's little play worth worrying about.
The parts list shows a grub screw in the ally slider.....I assumed it was for securing the slider tube to the casting, but perhaps it's to hold in the bottom bush? My factory manual doesn't mention replacing the bushes at all.

 

[Rusty Bolts]

A slide hammer like Tricky's seems the way forward. I have my other bike so I can take a bit of time over this. I'll see how I get on.
Cheers for the suggestions and pictures so far.

 

[King Key]

Can you put the bike on the centre stand and get someone to sit on the pillion seat so the front is unweighted and above the ground. Then pull back and forth on the base of the foks to see if there is any play in the legs, it would isolate any input from the brakes doing it like this.

 

[Rusty Bolts]

Can you put the bike on the centre stand and get someone to sit on the pillion seat so the front is unweighted and above the ground. Then pull back and forth on the base of the foks to see if there is any play in the legs, it would isolate any input from the brakes doing it like this.

Good Point King. I intend to unbolt the fork from the top yoke and then do what you suggest. That way any play in the top bush will be even easier to feel. Tricky's post alluded to play will almost certainly be in the top guide bush as that one is the furthest away from the two anchor points and subject to the most 'bending'. Plus I don't have to strip a fork leg off the bike to find this out.

 

[Bendy toy]

These bikes pretty much balance on the centre stand. Just put a jack under the engine bash plate.