F4i master cylinder upgrade
 

I put aftermarket stainless lines on my F4i, the 2 separate lines kit and they are way longer than stock so I need to upgrade my master to one with more power that pushes more fluid. Anybody here done this and want to recommend something that bolts right up? Master and reservior in one piece hopefully and I don't know if all banjo bolts are the same size for most bikes.

Why is it that you want to get a bigger master cylider? I did a similar install. I got the two nylon lines for my bike. You say yours are longer that stock? Like, there is a bunch or excess line between the master and caliper? If this is so, then you probably have the wrong lines. Mine are long enough to get to my calipers, but if I fully extended the fork, they would probably only have an extra half inch of length. So I would say you need different lines if they are too long.

Second, even if you stick with the lines that are too long, you do not need a bigger master cylinder. If you install them and bleed them correctly, then length or even diameter of hose does not matter. Your stock master cylider will always push enough fluid to move the pistons in the caliper. Even if your lines are too long, the same amount of fluid is going to flow thru them when you pull the lever.

Not really. I don't know you personally and I'm sure you're a real smart guy and might very well know a lot about bikes but in this case a lot of your post is wrong. Don't get mad, I wasn't born knowing anything, I've just learned as I go like everybody else. I'm sure you're just trying to help and thanks but in this case I do need a bigger master. It's actually a very common upgrade and of all the major OEM's and even aftermarket companies there exists every size bore and stroke master you could think of within reason. Certain theories by Bernoulli and other long decomposed scientists can seem to suggest that any size master would/could create equal pressure in a closed system since pressure is equal at all points in that system but its the amount of pressure that's key in my case. I can't run the brakes on my truck with a master off my bike even if the reservior from my truck was fitted to my bike's master. It's all a matter of strength where seemingly minute changes can result in major differences. Anybody that's upgraded please post up.

and I know a smaller bore would add more pressure, but I need different travel as well

K, good luck man!

I think you're defending a want, not a need. I have stainless all around, and my bike stops great with the stock master.

Granted you're perfectly welcomed to that want, but that's why ssweetbro probably said what he did...

Given the fact that you'd have to type a novel to completely explain the situation with a bikes behavior it makes it tough to get your point across sometimes. My bike stopped fine with my old rotors, lines, etc. Now with my new longer stainless lines it doesn't stop near as good even with the larger rotors and new pads. There is also no air in the system anywhere. I can't stress that enough, trust me no air. Want/need not an issue, my brakes are inferior due to the inferior master being the weak link in an otherwise upgraded system. Brake mechanics are complicated in principle given how different bore/stroke size/lever pull lengh/line capacity effects everything but its a common mod/swap I was hoping someone here had done it with OEM parts from other bikes rather than me having to go Brembo. Its really more of an absolute necessity I do this. Not trying to be an ass really, but why do they make 100 different ratios of bore/stroke etc if it makes no difference. P=F/A change one variable, change everything.

Hey man,

Check out this site. http://www.yoyodyneti.com/ I am trying to change a clutch master on a different bike and someone recomended it to me. Just type "master cylinder" into search and a ton will come up. Some are real expensive, but some are reasonable. Hope it helps.

thanks. heard of them before but couldn't remember the dyneti part of their name.

well you say you have new rotors and brake pads, did you even give the pads and rotors the time they need to break in before you think there is something wrong with your master. im just saying cause i upgrade my F4i master to a 954's just cause i wonted a radial cause of the amount of times i bleed my brakes, and honestly i can not tell the difference between the to. though i would have to agree with ssweetbro he's theory is correct.

You can't tell the difference because the bore and inner axis numbers are nearly identical on the 954 and F4i masters. In fact I think they are exactly the same on most 954's although some came with a bore maybe 1mm larger which would hardly be noticeable. You should have bought something that pushes more fluid and has a higher travel number. It was just a shot in the dark that someone would come by here who had dealt with this before. Anybody know of a 19x20 master that's not a Brembo? Anybody know what bore and stroke a 07+/- GSXR 1000 master has?