1150GS Pre-rebuild jobs/upgrades advice please!

[Bikermike1411]

Hi all,

I’m approaching the turning point in my restoration - for context it’s been sat idle for about 15 years, and has covered 29k miles. The bike is now stripped down to just the engine, gearbox, driveshaft and rear wheel, with a whole lot of engine painting and stove enamelling to be done before I turn the corner and start

Before I commence on the rebuild proper, is there anything you can recommend I should do now, or as I’m putting it back together?

For example, the clutch hose is nasty and will be replaced while I can easily access the slave cylinder, but I don’t know what to do regarding the slave cylinder itself. I’ve read that they can leak, and that the slave cylinder can’t easily be rebuilt and fitting a new one is the only real option. However, they’re not cheap, and I’ve not even had the bike in gear yet so I don’t even know if it works!

I’ve tentatively pencilled in looking at the clutch/shaft/diff for the second half of the project once everything at the front and in the middle has been addressed.

Do I bite the bullet and replace the slave cylinder preemptively? Is there anything way I can check whether it has failed?

Other than that, I’ve already decided to give the bike a servoectomy and replace the brake lines with braided hoses and possibly look at doing the starter motor jump-start modification. I’d like to source some crash bars to refurbish and fit, LED lights to mount on them, and I’ve got a FuzeBox to wire in for farkles and gizmos. I’d also like a CarPlay-type screen and mounting bar to use as a satnav.

I’d love to replace the shocks with some funky ones, but I don’t think I can get that past the bank manager.

What other either service jobs or quality-of-life upgrades should I do as I’m putting it all back together?

I’m hoping to keep costs down, and will have to prioritise based on this, but I’m sure there’s a lot I can do on a budget!

Cheers
Mike

 

[Paul Young]

Mike, I’m not sure where in Lancs you are, but I have an old set of Touratech engine bars in black that you might like to take a look at. I replaced them with stainless GSA bars and sump guard that I picked up for a song and the old ones have sat on top of our garage freezer for the last 10-15yrs.

FWIW, I’d bite the bullet and replace the slave cylinder whilst you have the chance to do it easily. It’s unlikely to be in the best condition after all this time… Worst case scenario, you could sell the old one on if it turns out to be ok.

 

[Bikermike1411]

Yeah, slave being a swine to access is another reason to consider swapping it out- plus if it hasn’t leaked then the clutch itself should be fine - it won’t be if the slave gives up on the first ride out next year…

Cheers Paul! I’ll pm you shortly regarding the bars

 

[Steptoe]

If you’re going to replace the slave cylinder then replace the oil seal that’s deep inside the recess, the input shaft, output end oil seal.
Thats the seal that leaks gearbox oil into the slave cylinder recess and which then runs along the clutch pushrod tunnel and ruins the clutch friction plate


Motorworks description -,The input shaft has two seals. This is the seal at the back of the gearbox under the clutch slave cylinder. It is a gearbox oil seal NOT a slave cylinder fluid seal.

 

[Bikermike1411]

Thanks Steptoe! Can I get at the seal through the aperture for the slave cylinder, is is it advised to do it with the clutch housing removed?

Regarding the slave cylinder and seal - is there any way to gauge their condition, or should I just replace them out of caution?

 

[Ian J Hartley]

Clutch slave cylinder.

It’s probably worth removing the slave cylinder whilst the bike is stripped to just examine it for possible leaks.

But the first sign of a failing clutch slave cylinder is when the fluid in the reservoir turns black with metal particles. When this happens the small thrust bearing at the end of the slave cylinder has failed and the whole piston is turning in the cylinder wearing out both the seal, piston and cylinder.

Ian

 

[Bikermike1411]

Thanks Ian! Can I check what you mean by the reservoir? Do you mean the reservoir at the master cylinder on the clutch lever, or the fluid behind the piston on the slave cylinder?

Just need to be sure where to check!

 

[Ian J Hartley]

Thanks Ian! Can I check what you mean by the reservoir? Do you mean the reservoir at the master cylinder on the clutch lever, or the fluid behind the piston on the slave cylinder?

Just need to be sure where to check!

Master cylinder reservoir on the clutch lever.

 

[Bikermike1411]

fluid came out dark brown - old, but not black….

 

[mikeyboy]

I’d replace all gearbox seals,
Mainly in order to pay good attention to the condition of the shafts where the seals run.
Corrosion can creep in , damaging the shaft surface.
Tis a ball ache having to sort leaky gearbox seals after the bike has been rebuilt

 

[Bikermike1411]

Cheers Mikey, can I do this in phase 2, after the engine and gearbox paint has been refurbished and front end is back in? That should allow me to strap the bike to the bench and remove the rear wheel and swing arm

 

[Hay Ewe]

Check all the wiring outer cover.
Known to decay over the years.
There is a spot on the LHS where the loom is tight against the frame and airbox.
I probably have a picture, will post later.

 

[Bikermike1411]

Thanks Ewe. The loom sheath completely disintegrated in places during the disassembly. I had black confetti all over the bench as I took the bike apart! It’s certainly getting repaired…..

I know the exact spot you mean on the left. Oddly, it actually seems ok there, but I’ll inspect it closely when I get to it!

 

[Hay Ewe]

And another, check and clean the earth point under the battery tray area, on top of the gear box.
And whilst there, check the condition of the rubber boot cover for the g/box breather.

 

[Hay Ewe]

And if in to it this far, all 4 cables connected to the Bowden / throttle splitter box.
Easier to do now.
Not there is a change to the twist grip cable rooting.
Details on MaxBMW page for that pn.
Cant find it?
Let me know and i shall post the link tomorrow

 

[Bikermike1411]

All good advice, thanks! This is exactly the stuff I need to be checking off!

Regarding the clutch slave cylinder, I whipped it off this morning. Got a bloody shock when i saw this…..





However, i’m 99.9% sure it’s crystallised grease. The clutch was replaced 8k miles ago so it could be from that job.

The slave itself seems remarkably mint - the bearing at the end is buttery-smooth and the pushrod moves freely

 

[Nin]

I think Denz0 on here can supply the internal seals that allow you to repair these slave units, rather than have to replace the whole thing.

 

[Udders]

Replace EVERYTHING you can while it’s completely disassembled.

 

[Bikermike1411]

Thanks all. Any thoughts on the condition of the pushrod? It came out easily, straight out. However, there’s a little bit of scoring at each end - it’s been gripped hard with pliers and twisted to remove it - I can see some marking at the slave-end and some scoring at the internal/clutch end. Will this interfere with the seal at all?

The condition looks ok besides this. I can’t tell if it’s got a Teflon-esque coating which might have worn in places.

 

[Hay Ewe]

Maybe change the felt seal on that and apply some of the white paste grease that comes with the clutch kit.
I beleive the felt seal is to cusion the pushrod from any whipping and to also slow or absorb and oil migrating down the shaft.