78 GS1000 master cylinder

[cjetmech]

Does anyone know of a front master cylinder that would be a direct replacement for my 78 Skunk? I’m getting my bike back on the road and found it leaking again. I rebuilt it once but the bore is pitted pretty bad. I’d just like to swap it out without doing a whole front brake upgrade. Thanks for any info.

[Nessism]

14mm piston for single disc and 5/8" for dual. Tons of options on ebay. If you have handlebars that angle down an EX650 master will work well. That's what I'm using on my KZ.

[cjetmech]

Thanks you sir.

[rphillips]

Don't know if orig. looks matter, but for the correct look, 1979 & before they used the round reservoir. 1980 up they used the square ones. Either should work fine, just look different.

[rphillips]

Just more of what he said. I just looked at the part #'s for the "79" 1000's. It shows a different # for the "L" models, that had dual discs, but taller, more angled, handlebars (ape hangers) & the "E" & "S" models that were also dual discs, but had a handlebar that is more level. The "L" master reservoir will not sit level on the orig. handlebar, nor will the "E" master reservoir sit level on an "L". Just say'in.

[cjetmech]

Well thanks for that info. Mine is an E with the round m/c. I was going to try and keep it original looking but after thinking about it overnight I’m going to do the whole twin pot upgrade. So now I’ve pretty much thrown keeping it original looking out the window. I figure I’d rather have better working brakes than originality.

[Grimly]

Just thought I'd toss my two lumps of coal in.
My favourite go-to master cylinder of 5/8" bore is the Nissin one fitted to the NVT 700 and 750. Nice feel, span-adjustable lever and fits on without fuss. Still looks quite good on the bars, too. Another big plus point is that's a genuine OEM one (albeit Honda) and you can be sure it's been made properly, out of decent materials. Even allowing for the cost of re-sealing it (if necessary) it's still cheap insurance.

[salty_monk]

I've used an EX650 one for years.... Cheap ($25-$40), good feel, adjustable lever & mirror mount. Not too modern looking, new enough not to have to rebuild etc. What's not to like?

They use a microswitch brake switch so you have to change the wiring. I put two spade terminals on the original wires after cutting them off & then a bit of black shrink wrap around that. I imagine a bit of fuel pipe or various tapes could be used too.

[tas850g]

I've used an EX650 one for years.... Cheap ($25-$40), good feel, adjustable lever & mirror mount. Not too modern looking, new enough not to have to rebuild etc. What's not to like?

They use a microswitch brake switch so you have to change the wiring. I put two spade terminals on the original wires after cutting them off & then a bit of black shrink wrap around that. I imagine a bit of fuel pipe or various tapes could be used too.

I’ve been using an ‘04 Sv650n MC for a few years which has the mirror mount. Had to do the electrical mod as Salty described.

[hannibal]

Just more of what he said. I just looked at the part #'s for the "79" 1000's. It shows a different # for the "L" models, that had dual discs, but taller, more angled, handlebars (ape hangers) & the "E" & "S" models that were also dual discs, but had a handlebar that is more level. The "L" master reservoir will not sit level on the orig. handlebar, nor will the "E" master reservoir sit level on an "L". Just say'in.

This might only apply to the 750s... A member here found that the angled reservoir on the 750L MC could be swapped out for the straight reservoir on the 750 non L. In other words, the difference between the 750 L and non L MCs lies in the reservoirs, which are interchangeable.

[mustangflyr]

M/C bore

On my 80 GS1000ET I had the M/C sleeved, works great.