Help choosing Master Cylinders

Discussion in 'Brakes' started by AMechEng, Jan 30, 2019.

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  1. Jan 30, 2019 #1

    AMechEng

    AMechEng

    AMechEng

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    I'm in the process of upgrading brakes on 06 vmax. Front will be 320 mm rotors, Hayabusa 6 piston on both sides, new lines (Goodridge Sniper 2), and new master cylinders for front brakes and clutch. Clutch will be DD. Trying to figure out which route to go on MC bore size. I previously used Nissin axial 5/8 for both and they work well. I would like to use radial now but they seem to only come in 19mm. What do you guys think about using Nissin 19mm Radial master cylinders with this brake setup and DD clutch?
     
  2. Jan 30, 2019 #2

    one2dmax

    one2dmax

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    19mm seems way too large? It may work with the increased piston volume but it's not going to have a lot of distance on the lever between starting to brake and fully locked up. Some may call this a "wooden" feel. I know there are charts out there to calculate this but I don't have that info on me.
     
  3. Jan 30, 2019 #3

    MaxMidnight

    MaxMidnight

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    You need to establish what the leverage ratio is for the different areaa of master cylinder to your chosen calipers.

    Have a read of this.
     
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  4. Jan 30, 2019 #4

    Fire-medic

    Fire-medic

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  5. Jan 30, 2019 #5

    mabdcmb@yahoo.com

    mabdcmb@yahoo.com

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    There are multiple sizes of radial master cylinders out there.
    First number is piston diameter, second number is stroke. A 19x18 master feels much different than 19x20.

    Piston diameters typically available. 16, 19
    Stoke distances typically available:15 thru 20 depending on brand and type.
    There may be different sizes out there. I'm not familiar with them all.

    Sean was (maybe still is?) an Accossato distributor. I jumped in on a purchase a long time ago. Its a nice unit, comparable to Brembo but cheaper and came with free brake lines during the promotion. I'm running a 19x18 and it works EXCELLENT with Gen2 Hayabusa radial calipers and rotors. Beware, I have noted that the Accossato lever is designed in such a way that it will contact the switch housing before the lever will bottom out against the grip. I've never had an issue with this on the brake side. Being I don't have it on the clutch side, I'm not sure if it would be a problem.

    On the clutch, I'm running a 2008 ZX-14 clutch master as recommend by Przemek/Satriel666 on this forum. I have a DD clutch setup. I've tried multiple different master cylinders. 14mm, 15mm, OEM... The ZX-14 master is my favorite by far. Clutch feel is very close to stock even with the DD springs. I do not know what the bore and stroke measurements are on this unit. The kawasaki PN is 43015-0115 if it helps you any. I bought mine used for a great price.
     
  6. Jul 24, 2019 #6

    MikeUSMC1371

    MikeUSMC1371

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    Alright, not to sound like a newb, because i've owned multiple bikes, but have never ran into this issue: I recently put drag bars on, but in order to do so, I had to cant the brake and clutch master cylinders back a bit to avoid the risk of some crazily bent brake and clutch lines.

    Question 1: Is it safe to have the reservoirs canted back without risking functionality? My theory is, the cylinders/fluid is under pressure, so therefore should function the same without risk of air getting into the lines anywhere, BUT, that's only a theory.

    Question 2: IF I were to go with one of the above mentioned options for alternate master cylinders and reservoirs, how did those of you that swapped yours, re-incorporate the 4 wire clips that attach from the control modules to the cylinders?
     
  7. Jul 24, 2019 #7

    MaxMidnight

    MaxMidnight

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    The fluid would only be under pressure when the lever is being pulled in.
    I guess it depends on how far back 'a bit' is. A photo would allow a more informed opinion.
    Provided the reservoir maintains the fluid over the holes into the m/c bore you shouldn't have any issues.
    There could be a problem if you loose fluid which uncovers the inlet to the piston.

    I'm assuming you are referring to the stop light and clutch switches?
    I used a hydraulic switch as a replacement.
     
  8. Jul 25, 2019 #8

    Fire-medic

    Fire-medic

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    You don't want the brake fluid to be below the minimum mark. Doing so will risk sucking air into the system, and there-goes your braking efficiency. I don't know if you're speaking about the Gen. 1, but I only have two wires from the front brake master cyl. Brake side two wires are to actuate your rear brake light. They are two smaller size spade terminals. You should be able to run a jumper wire to confirm that the switch on the brake cyl you fit will actuate your brakes correctly. I like leaving things un-cut, so I'd adapt a permanent jumper to allow returning to the OEM equipment.

    On a Yamaha literbike, I soon discovered that I had to position the bike a certain way to be able to fill the brake and clutch reservoirs without risking air in the system. I kept getting a too-much travel lever, and it took me awhile to figure out the system was allowing air into the system at being parked at full-left-lock, and with a just-low-enough fluid level to allow air infiltration, though there was fluid in the reservoir window.
     
    Last edited: Jul 25, 2019

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