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Clutch Master Cylinder

Old 06-23-2016, 10:01 AM
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Clutch Master Cylinder

Hello all! I have a SuperHawk with 55K miles. It seems as though the brake master cylinder is finally failing, so I am looking to replace both master cylinders (brake and clutch) with new aftermarket radial units.

I would like to know what size the stock Clutch Master Cylinder is on the bike. I am not able to look at the bike right now, hoping someone either knows the answer from memory or can pop out to look at the markings on the clutch master cylinder.

Thanks!

-Tom
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Old 06-23-2016, 10:43 AM
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Did you try the search function?
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Old 06-23-2016, 11:33 AM
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14mm.
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Old 06-23-2016, 11:40 AM
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Originally Posted by IL8APEX View Post
Hello all! I have a SuperHawk with 55K miles. It seems as though the brake master cylinder is finally failing, so I am looking to replace both master cylinders (brake and clutch) with new aftermarket radial units.

I would like to know what size the stock Clutch Master Cylinder is on the bike. I am not able to look at the bike right now, hoping someone either knows the answer from memory or can pop out to look at the markings on the clutch master cylinder.

Thanks!

-Tom
clutch is 14mm

But why replace? repair parts are cheap unless the bore of the OEM one is damaged.
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Old 06-23-2016, 11:45 AM
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Originally Posted by VTR1000F View Post
14mm.
You helped him break the third rule of SHF.
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Old 06-23-2016, 12:20 PM
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I did try the search function... Must have been too specific, as I didn't come up with the number.

Thanks for that, VTR.

Marquez- for the time invested in a rebuild I'd rather just buy something that will work another 15K miles, rather than get the old ones apart and find the bores are tired. Simple time vs. money equation.

Anyone else think it's interesting that the clutch and brake bore diameters are similar? I would have thought the brake bore would be larger, as that seems to be the trend in modern bikes.

Anyway, it seems that I can get a reasonable quality Master (Magura, Braking, etc) for about $200. Not free, but not Brembo territory either. I considered another bike, maybe low mileage OEM Aprilia takeoffs? Anyone care to recommend a modern hydraulic clutch motorcycle I could look for? (I'm used to sport bikes and dirt bikes, they all seem to be cables.)

-Tom
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Old 06-23-2016, 01:44 PM
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The master cylinder bore has to relate to the size of the slave cylinder and how much travel it needs to have in normal use. The clutch slave has to move a fair distance to disengage the clutch plates, so you need a large master to smallish slave ratio. For the brakes, while you are moving 8 pistons, these only need to move a short distance, and you need a large ratio between the area of the slave pistons and the master, to provide hydraulic leverage i.e. to multiply the force that you exert on the lever.
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Old 06-23-2016, 02:22 PM
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Originally Posted by Just_Nick View Post
You helped him break the third rule of SHF.
They're my rules. I'll impose them when and where I see fit as any jackass making rules should do.
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Old 06-23-2016, 02:43 PM
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Originally Posted by IL8APEX View Post
Hello all! I have a SuperHawk with 55K miles. It seems as though the brake master cylinder is finally failing, so I am looking to replace both master cylinders (brake and clutch) with new aftermarket radial units.
Be careful what you wish for. Because of my height, I wanted the levers lower down (rotated forward). To do this it required radials because the snout of the axial setup prevented the lowering. Radial levers have a section past the pivot bolt that activates the switch. This hits the fork by 1/4 travel. Convertibars were purchased. Too high and hit the fairing at almost any position, Too far forward and the back end of the lever hits the speedo surround. So I have machined the Convertibars down by about 15mm, and the left switchblock still hits the fairing at almost any position. I have had to set them up in a position quite close to the factory position, but don't really have a choice. By the time I had them landed in Oz - $600, not happy about that. I have spent hours just sitting on my bike trying to see a solution (to the point I nearly torched it & bought an RSV4R) - not kidding there - so really consider what the problem is, and is it worth it to make significant changes.

Originally Posted by IL8APEX View Post
....for the time invested in a rebuild I'd rather just buy something that will work another 15K miles, rather than get the old ones apart and find the bores are tired. Simple time vs. money equation.
Partzilla - clutch master internals $40, brake master internals $28 ($38 pre '05). Drain system, remove master from bike, push plunger in, remove circlip, wipe out bore, inspect carefully, coat new rubber bits with brake fluid, install new internals, push down on plunger, install new circlip, refit to bike, fill and bleed system. Can't see any reason why bore would be damaged as its only rubber and brake fluid present. Whole job should be done in a couple of hours.

The other thing to consider is master cylinder size. It has been covered widely about increasing brake master size without increasing caliper size can make brakes feel a bit crap. Because of the different action of a radial, a 14mm radial master will have more braking power than a 14mm axial, so you may feel **** brakes.

*BTW the master on the bike will probably say 7/16 rather than 14*
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Old 06-23-2016, 04:25 PM
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Originally Posted by Twitchy View Post
Partzilla - clutch master internals $40, brake master internals $28 ($38 pre '05). Drain system, remove master from bike, push plunger in, remove circlip, wipe out bore, inspect carefully, coat new rubber bits with brake fluid, install new internals, push down on plunger, install new circlip, refit to bike, fill and bleed system. Can't see any reason why bore would be damaged as its only rubber and brake fluid present. Whole job should be done in a couple of hours.
Good idea, wish i had thought of it.

Short of water (the fluid is hydroscopic after all)in the fluid, no damage to the master cylinder is likely..
Time vs Money actually speaks to rebuilding.. a 20 min task at best, plus another 15 to bleed. If I were to do it, Id get a new seal for teh salve and disassemble, clean, refit that as well and well, Id add a new SS line while it was apart.
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Old 06-23-2016, 04:37 PM
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If you're absolutely set on replacing both MCs, you can always get a Ducati OEM Brembo unit on the clutch side (15x18; what I have been running for a few years now) and, if you are still running stock front brake calipers, an OEM Yamaha/Brembo radical brake MC (a 16x18 IIRC) from various R6 and R1 models (ones with the 4-piston Sumitomo calipers as they have the same piston sizes as the VTR's Nissins).
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Old 06-23-2016, 04:38 PM
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Originally Posted by E.Marquez View Post
(the fluid is hydroscopic after all)
Umm.. that would be hygroscopic

Originally Posted by E.Marquez View Post
.. a 20 min task at best, plus another 15 to bleed.
Geez, I think I need to work a bit faster!!!
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Old 06-23-2016, 04:48 PM
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Originally Posted by Twitchy View Post
Umm.. that would be hygroscopic


Geez, I think I need to work a bit faster!!!
What can I say My phone does not know the word hygroscopic but apparently knew "hydroscopic" lol....

As for time..... I do this every day.....literally.. knowing the right tools to reach for the first time, all at arms length, Right tools in a known spot in the cart, parts on hand, sonic tank already on and warmed up.. Yes its that fast..
But even at 3 times as long... still likely less time that playing mix and match with aftermarket or other model OEM parts to get something up and running.
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Old 06-24-2016, 08:53 AM
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Originally Posted by mikstr View Post
If you're absolutely set on replacing both MCs, you can always get a Ducati OEM Brembo unit on the clutch side (15x18; what I have been running for a few years now) and, if you are still running stock front brake calipers, an OEM Yamaha/Brembo radical brake MC (a 16x18 IIRC) from various R6 and R1 models (ones with the 4-piston Sumitomo calipers as they have the same piston sizes as the VTR's Nissins).

You're definitely on the same page as I am with those suggestions. Should be plenty of examples available.

Going back a bit, am I wrong to assume the anodized finish is worn from the inside of the M/C bores after 55K miles?

-Tom

Last edited by IL8APEX; 06-24-2016 at 10:52 AM.
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Old 06-24-2016, 02:45 PM
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I think this is an interesting thread if you're going to start playing with your brakes. Later in the thread there's some interesting info about MC size and piston area, etc.

https://www.superhawkforum.com/forum...ke-mods-13176/
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