Run only single disc/calliper on '75 twin disc

[TimMac]

Am I able to 'cap' one calliper and run only a single disc on a twin disc 75 XS? Maybe even remove one disc?

I've completely rebuilt and replaced each calliper with all new parts and still have a leak in one calliper, so I'm unable to get any pressure in the lines.
I've grease gunned it so many times now to pop the pistons out that I'm almost ready to kick it over and set it on fire.

 

[RustiePyles]

Am I able to 'cap' one calliper and run only a single disc on a twin disc 75 XS? Maybe even remove one disc?

I've completely rebuilt and replaced each calliper with all new parts and still have a leak in one calliper, so I'm unable to get any pressure in the lines.
I've grease gunned it so many times now to pop the pistons out that I'm almost ready to kick it over and set it on fire.

Yes, almost all US bikes were built and shipped with only one front disc, not a problem.

 

[gggGary]

Short answer is yes.
but original dual disk bikes used smaller rotors, so you may not be happy with how much brake you have when it's really needed.
If it was converted from a single rotor to dual rotors then you'll be back to the original (lackluster) brake. This has more to do with the large MC bore often used in the early days of disk brakes, than with inadequate brake area. Changing to a smaller bore MC is nearly universally seen as an improvement.

PS complete aftermarket callipers are available.

 

[gggGary]

pps after one disassembly you should only need a bit of air pressure to pop the pistons out, cover pistons with a rag to prevent mayhem.
Do the pistons slide freely in and out of the bores when the seals are removed? Seems we had one guy with repop pistons that were too big.

 

[TimMac]

I don't have an air gun so I've resorted to using a bolt and sleeve nut to walk it out, and when that doesn't work I use a grease gun which is a terrible time.

Do the pistons slide freely in and out of the bores when the seals are removed?

The pistons appear to be the same size as what I pulled out of them, and the new ones move freely without the o-rings, although there is some pitting inside the grooves due to rust, so it's either that or the pistons are too short and are seating into the piston too much.
I marked one of the pistons yesterday, so I'll try to run her with just one disc.

PS complete aftermarket callipers are available.

In hindsight, I should have purchased entirely new assemblies. The cost of new pistons, seals, bleeding screws, and the time spent, worked out to be more expensive.

 

[gggGary]

You don't have a way to inflate a tire?
It takes very little air to pop out the pistons. I don't think they can go too deep.

 

[TimMac]

I can just see the top of the o-rings when the pistons are fully seated.
I just inflate my tires at a gas station. I was going to buy an air compressor but I brought a grease gun instead because they have like 4500 psi. The pistons were seriously rusted and I'm trying to keep this under $400.

 

[fredintoon]

I can just see the top of the o-rings when the pistons are fully seated.
I just inflate my tires at a gas station. I was going to buy an air compressor but I brought a grease gun instead because they have like 4500 psi. The pistons were seriously rusted and I'm trying to keep this under $400.

Hi Tim,
air compressors are like flush toilets, once you've tried one you'll never go back to a whistle & thud.
Alas, collecting air tools can become an obsession.

 

[arcticXS]

I have one of these on my RD350:

https://www.economycycle.com/shop/y...er-front-rd250all350all40076-78-reproduction/

A pretty significant reduction of unsprung weight, at a reasonable price. I use a 13 mm Brembo MC with this caliper on my RD (a single 267 mm disc is plenty on the RD.
On an early XS like yours, a single 298 mm disc, with a stock caliper or this repro one, with a 13 mm MC should be enough. If you really want or need a dual setup, I'd definitely recommend 2 repro alloy calipers, and thinner, drilled discs, and a 16 mm MC.
The OEM brakes from this era are ridicoulusly heavy.
On my 77 XS, I replaced the OEM dual discs with a single 320 mm custom made ISR disc, a 4 pot Brembo caliper from a 90s Ducati, a single brake Line and a 13 mm Brembo MC. I also fitted an aluminium front fender. Altogether I reduced unsprung weight by 5 kg (12 lbs) Saying that the front suspension was vastly improved is an understatement!

 

[650Skull]

I can just see the top of the o-rings when the pistons are fully seated.
I just inflate my tires at a gas station. I was going to buy an air compressor but I brought a grease gun instead because they have like 4500 psi. The pistons were seriously rusted and I'm trying to keep this under $400.

Buying tools cant be added to the cost of a build............The tool cost can be offset against the cost of paying a mechanic to do the job.............Money saved on the mechanic, buys a lot of tools and once a basic set of tools are bought, that cost stops.............taking a bike to the mechanic every time something goes wrong, the cost never stops...........

Priority when buying tools............a compressor is an all round handy tool that can cover a multitude of jobs............... a grease gun is very limited in what it can cover.

after a Caliper has been disassembled and reassembled there should be no need to use any other tool to remove the piston again, except the normal use of the brake lever.

If the piston is stuck, and has to be removed by the use of the grease gun again, i would say your brakes are not working properly, having to force the brake handle to operate a stuck caliper piston is going to cause your brace system to find a weak spot and leak from that.

 

[TimMac]

On an early XS like yours, a single 298 mm disc, with a stock caliper or this repro one, with a 13 mm MC should be enough

I took it for a spin with just one disc and it feels adequate for how I ride it, I also replaced the rear shoes so it's stopping much better. Should keep me upright until I get some more play money to improve on it.

 

[650Skull]

I took it for a spin with just one disc and it feels adequate for how I ride it, I also replaced the rear shoes so it's stopping much better. Should keep me upright until I get some more play money to improve on it.

Disconnecting the faulty Caliper will make the brakes work better. Being a twin disk, if one caliper piston is Hard to move, it will affect your braking power.

 

[arcticXS]

Just to be clear. RD 350/ 400 (except 400F/ Daytona) had the same caliper as XS2- TX650- XS 650C.
The floating calipers from 77 onwards were a step backwards IMHO. I guess the beancounters overruled the engineers......