Twinpot Brake upgrade on 78 Skunk

[Grimly]

If you re-bleed and the problem is still there, then check for lost motion in your calipers and pay particular attention to wear in the sliding pins/holes. It's just in the nature of sliding calipers that wear happens and it's possible the ones you got might be high mileage.

 

[mattfeet]

They only had ~8k miles on them, single owner bike. To verify, where specifically are you talking about?

Matt

 

[Grimly]

They only had ~8k miles on them, single owner bike. To verify, where specifically are you talking about?

Matt

Where the body of the caliper is mounted to the bracket, it's coupled via a pair of sliding pins - either the pins or the hole in the bracket wears, or both do. 8K miles is likely ok though, but if they were never properly lubed or checked, who knows what state they're in.
Is it similar to this one, from an '88 ZX600?

 

[mattfeet]

Yea, same caliper. I took them apart, re-lubed, and replaced all seals when I got them. Everything there looked ok to me but I also wasn't looking for damage, either.

Matt

 

[Grimly]

If the pins have more than a smidgeon (technical term) of side-to-side play, that will translate into lost motion as the caliper will rock on the pins initially. As the caliper and pads bed in, it might even improve a bit, but the wear is still there. Eventually it will lead to uneven wear on the pads and they'll wear in a wedge shape, leading you to dumping the pads before you get the full mileage out of them.

 

[mattfeet]

So you're saying if I can, with the caliper assembled, feel side-to-side play in the caliper then I made need to look for a new set?

Matt

 

[Grimly]

When you remove it, if you feel side to side slop in the caliper/bracket, then it's not good.
The fit of the pins in the holes is what counts - if the holes aren't worn, but the pins are, you could get new pins. If the holes are badly worn, the bracket is likely scrap. Again, at 8K, I'd suppose they'd be ok. The main body of the caliper will be ok, though.
This is a weakness of all sliding calipers and the ones on bikes, being alloy-bodied are more prone to it - car calipers in cast iron sharing the same design don't get it so badly.

However, however; having said all that - if you re-bleed and don't see any lost motion or rocking when you squeeze the brake lever, then let the pads bed in. It might just be necessary for components to wear to each other a little bit and what wear there is might be minor enough to not cause any problems.

 

[mattfeet]

What other bikes share the same forks as the GS1000? I just bought a 1000C with single disc so, once again, I need to get new forks. I think the 850's are also 37mm so they should work, right?

 

[Grimly]

I bought single-disc GS1000 forks with the aim of swapping the almost perfect stanchions over to my dual-disc lowers. 37mm is right, and as far as I can see, the length is the same. I'm just hoping there's no gotchas with it.

 

[mattfeet]

You should be good. I did read in an old thread that the tripe tree spacing is different with dual disc bikes on the 1000...is this something i need to worry about doing the salty monk upgrade? I didnt swap an entire front on my 750 (just used dual disc forks on my original triples) so I find it hard to believe I need to swap an entire new front onto the 1000.

 

[salty_monk]

I am currently using 1983 GS1100E fork legs in my stock 78 1000 triples if that helps.

 

[mattfeet]

Was your bike originally single or dual?

 

[mattfeet]

Salty - do you have any brackets left? Tried sending a few PM's but haven't received a reply.

Thanks,
Matt

 

[salty_monk]

Yes - plenty left. Just been travelling a lot - Sorry! PM back.

 

[mattfeet]

Did some work on the 1000 today. Rebuilt fork lowers that Chuck Hahn sent me. Powder coated them, new seals, new fluid, new caps. Then I mounted up the CBR900RR rotors:

Mounted:

That's where I'm at right now. Tomorrow Im going to be installing the lines, calipers, pads, and taking her out for a spin.

 

[mattfeet]

Also - the 900RR rotors have the right bolt spacing but they just need widened a bit. I much prefer them to the CBR600 F3 rotors.

 

[steve murdoch]

Still love the look of of dual rotor spoked wheels.

 

[rudeman]

Another member of the Salty_Monk twinpot conversion team. I borrowed the stainless lines that were on it for another project but you get the drift.
I have not had the bike out so i cannot comment on the braking improvement, YET.

Is that a Kerker pipe?

Sharp ride. Spokers look sweet with twin drilled rotors.
Nice 'garage" as well...

 

[06-8-ball]

So the 900rr rotors bolt right up to the wheels? What year 900rr also what year and model calipers should I be looking for on Ebay? Also, do I need a new master Cylinder?

 

[Guest]

So the 900rr rotors bolt right up to the wheels? What year 900rr also what year and model calipers should I be looking for on Ebay? Also, do I need a new master Cylinder?

I can't say for sure on the 900RR rotors, but it will be the early years when they were still 900's before the displacement started creeping up. There are a host of bikes that use those calipers, have a look at the EBC brake catalog for all the fitments. The calipers use pad #FA129, shown on page 250 of the catalog:

http://www.ebcbrakes.com/Assets/ecatalogues/2014-US-MC-Catalog/2014-us-mc-catalog.html

You shouldn't need a new M/C if you already have twin discs on your bike.


Mark