Master Cylinder Rebuild?

[Valguard]

Have a GSXR 600 07 and I have never been satisfied with the front brake. I have braided lines and change the fluid often (I have a bleeding kit/pump thing and feel confident no air is in the lines). It just never feels very firm at the lever and I can always pull it back to the throttle, granted, with some muscle. I went to a dealership just to see if thats how all Suzukis are. I got a wide range of results but overall they are not nearly as firm as others, like Ducati or Honda.

Is the master brake cylinder on my bike just not very good? Would a rebuild help if perhaps some seals are damaged? Or, should I just spend the money and get a more top quality one? It's not that my brakes don't work, just not a good feel IMO. Anyone else out there experience the same problem on GSXRs or am I just crazy? Any help would be appreciated. Thanks!

[MetaLord 9]

Lemme get the stupid question outta the way first, do you have adjustable levers and have you adjusted them?

[UglyDogRacing]

The old suzuki cylinders sucked. Either upgrade to a newer Suzuki oem radial master cylinder or a Brembo.

[MetaLord 9]

If so and you've adjusted them all the way out, then I'm assuming the "feel" you're talking about is a squishyness. If that's the case, then it's possible you have a leak somewhere or seal that might not be too reliable. It could be the cap on the master cylinder, it could be the bridge from one line to the other, it could even be really worn down pads.

I'd look at things in this order (if it were me):
- check the pads for life
- check to make sure that both calipers close down evenly and effectively
- check the cylinder cap for snug fit
- check all connections (especially the rubber ones) for any leakage or weakening
- check your master cylinder & calipers for leaks

If you find nothing, you may want to consider the rebuild kit which, to my knowledge, is basically just a bunch of seals and a few internals if that.

[OUTLAWD]

The old suzuki cylinders sucked. Either upgrade to a newer Suzuki oem radial master cylinder or a Brembo.


the MC was the first thing I junked on my gixxer...I went with a factory brembo off an R1. I forget the internal dimensions, but it bolted right up to mine and I even used the yamaha light switch. Got the whole deal off ebay for ~$50

[UglyDogRacing]

I have braided lines and change the fluid often (I have a bleeding kit/pump thing and feel confident no air is in the lines). It just never feels very firm at the lever and I can always pull it back to the throttle, granted, with some muscle. I went to a dealership just to see if thats how all Suzukis are. I got a wide range of results but overall they are not nearly as firm as others, like Ducati or Honda.



How do you have your braided lines routed? Do you have stock routing: one line off the master cylinder to the right caliper and then another from the right caliper to the left? Or do you have 2 lines off the master cylinder, one to each caliper?

[Valguard]

ok:

- Yes, the levers are set as far out as possible.
- No, there is no leaking from anywhere. The pressure that is there is consistent and I never loose fluid.
- Cylinder cap is snuggly fit.
- Pads are Ferdo OEM equivalents with good life left.
- Routing is not stock. I have 2 lines off the master cylinder. One to each caliper.

Would the routing play a role? UglyDogRacing and Outlawd, sounds like these MC are just not up to snuff. If it's as easy as spending $50 to get a new one that sounds like the best option, if that's really what the problem is.

[UglyDogRacing]

ok:

- Yes, the levers are set as far out as possible.
- No, there is no leaking from anywhere. The pressure that is there is consistent and I never loose fluid.
- Cylinder cap is snuggly fit.
- Pads are Ferdo OEM equivalents with good life left.
- Routing is not stock. I have 2 lines off the master cylinder. One to each caliper.

Would the routing play a role? UglyDogRacing and Outlawd, sounds like these MC are just not up to snuff. If it's as easy as spending $50 to get a new one that sounds like the best option, if that's really what the problem is.

Yes. I've tried it many times in the past with the stock Suzuki master cylinders and you will lose alot of the pressure from the lever running 2 lines off of it. The stock master cylinder is not designed for it and will not create enough pressure when engaging the lever. Get a larger radial mc off of ebay.

[CaneZach]

Jim, I need to replace the MC on my 06 GSXR600 for this season. Do you remember which years Brembo made the MC for the R1's?

[UglyDogRacing]

Jim, I need to replace the MC on my 06 GSXR600 for this season. Do you remember which years Brembo made the MC for the R1's?


I believe 04 and newer.

[Valguard]

Sweet. Thanks for the help. Ill be on the look out for a Brembo MC off an 04 and newer R1.

[UglyDogRacing]

Sweet. Thanks for the help. Ill be on the look out for a Brembo MC off an 04 and newer R1.

The latest generation R6 came with them too.

[OUTLAWD]

Sweet. Thanks for the help. Ill be on the look out for a Brembo MC off an 04 and newer R1.


Mine took a few weeks of ebay scouring, i'm looking for one now for the triumph...some guys think they have gold and want $200+ for the "yamaha" brembo...for that I'll just buy the real deal, either brembo or accosato

[eklew]

I've got a stock one on my 02 Gixxer and it seems to work great. I just had to bleed it very well.

[OUTLAWD]

I think Jim's comment about it not feeling right with the dual lines from the master hit the nail on the head, the master wasn't sized to move that extra volume

[Kim-n-Dean]

I think Jim's comment about it not feeling right with the dual lines from the master hit the nail on the head, the master wasn't sized to move that extra volumeI bet Dirk can show the math on this. Two lines from the MC vs. one line to the caliper and one from caliper to caliper would still move the same amount of fluid and have to create the same amount of pressure. Off the top of my head, I would say there is no difference between the two set ups. Sounds like Suzuki MC's just aren't that strong.

[UglyDogRacing]

I bet Dirk can show the math on this. Two lines from the MC vs. one line to the caliper and one from caliper to caliper would still move the same amount of fluid and have to create the same amount of pressure. Off the top of my head, I would say there is no difference between the two set ups. Sounds like Suzuki MC's just aren't that strong.

I never said the amount of fluid was greater. It's the same. I am no physicist like Dirk so I can't give you the math, but I would bet that to maintain the same amount of pressure with two lines coming off would require a larger diameter mc.

[Kim-n-Dean]

I never said the amount of fluid was greater. It's the same. I am no physicist like Dirk so I can't give you the math, but I would bet that to maintain the same amount of pressure with two lines coming off would require a larger diameter mc.Either way, it doesn't matter to me. I ride a Yamaha.:D

Since braided lines aren't supposed to expand that much, let's remove "line expansion" from the equation. So, why would it take more pressure if you use two lines? Whether the line splits at the caliper or the MC, it still sends the same amount of pressure down the line. Or, is that exactly what we are talking about, line expansion? The longer the line, the more it can expand. Therefore, one line from MC to caliper and another to the other caliper is the shortest route possible, so less expansion over the entire system.:dunno:

[Valguard]

Hmm, yea the more I think about it mathematically it seems that having two straight off the MC would not cause a this problem. The slave and the other pistons are the same, the lines being changed should not make any difference. This leads me to believe that:
1. The master cylinder is just shitty to began with and I never really took notice until I felt a good one.
2. While changing my lines a while ago, I somehow got air in a deep dark place that fails to be expunged with normal bleeding procedures. (poor suzuki MC design?)
3. My MC has some damaged seal caused by _________ (fill in the blank).

Either way, a new MC would fix all these issues. It's seems like the quicker but perhaps insignificantly more expensive option and would leave me a better brake feel over the OEM Suzuki one in its best state.