Putting single front disc on gs1000

[Hango]

Lucky me, I have 2 1978 gs1000’s. Both were E models with mag wheels and dual front brakes. I am in the process of converting one to a c model. The c model has wire wheels and 1 front disc. With the single disc Why does the front brake lever now need extra extra extra squeeze? I was told that the master cylinder was,designed for dual discs. I also see that the E and C master cylinders have different part numbers.
Ok experts what do I do?
thanks

[fbody_mike]

So you took a dual disc set up and deleted one of the discs? When you did that you effectively reduced the leverage that was present at the master cylinder. Think of it this way, the area of the master cylinder piston stayed the same, but you reduced the total area of the caliper pistons by half. Its like moving the pivot point on a lever closer to where you are doing the work. Now when you squeeze the brake lever it takes less movement (travel) but more force to get the same clamping force on the disc. The easy solution is to change the master cylinder to the C version, it probably has a much smaller bore than what you have now.

[Sandy]

Single disk brake models have a different size piston in the master cylinder (smaller IIRC) and a larger piston in the caliper as well as the actual disk itself is a larger diameter. Nothing in common between the two expect for maybe the banjo bolts, brake line and the cap on the master cylinder.

[Nessism]

Need new forks legs, master, and disc. Hopefully you updated the brake lines too.

[salty_monk]

The single is 14mm the dual is 5/8" (16mm). Don't ask me why one is marked in metric & the other not...

The single brake runs on a larger rotor & in practice performs almost as well as the duals (i.e. terribly) in most circumstances... If you just deleted one of the smaller rotors & are running one dual I can't imagine how shi*te your brakes now are...

The wire wheels will run a second rotor. Sometimes you have to tap the holes deeper. They are under the plastic cover.

Dan

[Hango]

I have the correct fork legs, have found the correct rotor, I will get ss brake lines.
Where do I get the master cylinder? I’ve looked and looked.
Btw I am getting a tank tail and under seat painted burgundy with the correct decals, I like the look. No road racing with this bike.

[uk gs nut]

What Sandy said is right on the money !

[Agemax]

single disc up front on my GS1000. RF900 disc, ZX9R caliper and B12 m/c. s/s hose. Stops better than the original twin disc set up.
washed gus.jpg

[salty_monk]

I have the correct fork legs, have found the correct rotor, I will get ss brake lines.
Where do I get the master cylinder? I’ve looked and looked.
Btw I am getting a tank tail and under seat painted burgundy with the correct decals, I like the look. No road racing with this bike.

Tough to find an original with the round reservoir I would think...

One from a Ninja 250, KLR 650 etc would work & not look too out of place. Your dual one has a bigger bore (5/8" instead of 14mm). You may find it works but the lever travel will be a lot shorter. I've never tried it that way around...
Personally I would at least use the later caliper with the rectangular pad rather than the round one... (You could also use a Twinpot Tokico on a bracket with that larger rotor if you switched back to your old fork leg but then it wouldn't look standard).

[greg78gs750]

hard for me to imagine wanting to make a gs's brakes worse?

[Hango]

When in doubt I go to the experts. I now have 2finger lock up front brakes. Changing the MC and ss lines did the trick.
thanks all
jim

[garyS-NJ]

your GS is gorgeous. do you have a build thread? interested in your suspension/wheels/brakes