aftermarket/alternative front master cylinder

[jeffe]

I replaced mine with a M/C off a either a Radian or Fazer. It was a crashed bike. Works great, also lower profile.

[thewiz]

I replaced the original M/C on my SF recently with a Parts & More unit that their catalogue states is for a dual caliper system. The reservoir was noticably smaller (a pain while bleeding) and frankly I had never been satisifed with the pressure. Bled 'em to death. No idea what the piston diameter is/was. Guess I could measure it. No matter now cuz it's now broken completely , FUBAR, so I'm replacin' it with an rebuilt original and SS lines.

[somesuch]

Hi Alan,

I have rebuilt the calipers using McKay hydraulic cylinder assembly lube., something I do all the time when I rebuild calipers. It makes for easier assembly, less corrosion, and just plain makes me feel better

All the parts were in perfect shape, bores, pistons, seals....all were perfect.

I have now tied the lever to the bar for a couple of days, with no improvement the lever feel is not terrible, it just is not rock-solid that I expect from a 3/4 MC with SS lines.

Changing to new EBC pads made the lever surprisingly firmer ????

There may be an area in the caliper where the bubble hands, and makes it impossible to completely bleed the system.

I think I will start really looking at getting my GSXR frontend on the XS11 or at least getting different calipers on. My current SF calipers flex a lot! You can feel, and see them spread as you pull the lever.

--Nick

[John]

Nick

I have a good trick for bleeding the front M/C. It may take an other set of hands, so grab your spouse, or a buddy. First remove the right caliper, and let it hang for a minute. Next remove the M/C from the handlebars, and have your assistant rotate the M/C so that the lever is pointing straight up. Hold it like that while you take a suitable tool, a C clamp or large channel locks, and compress the piston back into the caliper. By inverting the caliper, that will allow that last little air bubble that is trapped in the banjo bolt to escape and be forced into the reservior when the piston is compessed.
It's worked good for me everytime I did it.

[somesuch]

Thanks for the tip John, I have tried something similar, just pushing the pistons all the way back, one at a time, and as far as the MC goes, I have a little bleeder on mine now since it is a radial one from a GSXR. Ill try wiggling the calipers around while pushing back on the pistons to see f it helps.


Some brake systems are so nice as far as bleeding goes. I remember putting a different MC on my older gsxr and just taking off since i was late for a ride without bleeding, knowing that the whole thing will bleed itself after a few stops

--Nick

[AlanB]

Hi Nick,

Hydraulics are just levers; a bigger piston will shift more fluid, but at lower pressure than the original. You should have very little movement, but need more lever pressure to get the brakes to work.

Have you had the bike out on the road, or are you just trying it on the bench? A brake will usually "run-in" in a few miles. The surface irregularities will smooth off, and the feel of the lever will become much more positive....... Try it!

Hope you get it sorted out.

AlanB

[somesuch]

Allan, in theory, the pressure/area relationship is how it is supposed to work, but from experience, radial master cylinder offers a much improved feel/lower effort despite having a larger bore.....i don't know how it is possible, and I was a skeptic myself until I tried both on the same bike. Brembo explained it through better efficiency and lack of change of direction of force (change of force direction is inefficient)



I took the bike out around the block and the brakes are better than with a stock MC, just not as good as I want them to be.

Has anybody ever got the SF brakes to have a rock solid lever, like 1/4" movement?


--Nick

[AlanB]

Hi Nick,

The brakes on my own SG work fairly well..........



Your comment of how the feel of the brake changed with new pads is possibly leading to the answer; if the bike is better than stock, then run it for a few hundred miles then report again; full bedding-in might take that long.

Changing pads, lines and master can only do so much; If you want it to behave like a modern system you may need to go to modern calipers too. Several bikes on the forum already have more modern brakes and front-ends. A search should give you all the encouragement you need.........

AlanB