Front Brake Master Cylinder

When I purchased my bike, the previous owner had done several small mods to the bike that I assume were meant to improve the bike. One of those mods is the use of braided brake lines and what appears to be a later model GSXR master cylinder/handle. With the purchase, I received the original Kawasaki master cylinder and handle, both in really good shape. My question is pretty simple: am I doing myself a disservice by going back to the original MC? I want to mainly for the originality and because I like the handle much better with it's finger grips. Will the feel be any different? Will it make any difference at all?

As long as the original master cylinder is in good condition there should be no problem. One thing to do is to make sure it is the correct one for the brake system on your bike. If you bike has dual front disks the master cylinder should be marked 5/8. Mine is marked on the bottom:

I'd take the master apart and inspect the bore for pitting and corrosion. Brake fluid absorbs water by design, but if you don't change the fluid every few years the fluid will corrode the system parts. Pitted master cylinder bores is very common so don't assume too much about the condition of the parts until you inspect.

Nessism wrote: I'd take the master apart and inspect the bore for pitting and corrosion. Brake fluid absorbs water by design, but if you don't change the fluid every few years the fluid will corrode the system parts. Pitted master cylinder bores is very common so don't assume too much about the condition of the parts until you inspect.

I should have mentioned that when I said it's in good nick: it's spotless inside. I've already pulled it apart and looked inside.

Since the Japanese industries don't use an inch or foot scale, what is the significance of 5/8? It's hard for me to believe that means 5/8 of an inch so what does it mean ...anybody know?

It does seem odd, but I think it does denote 5/8 inches. That equals 15.875mm. Ed

The 81 650-CSR w single disk Fr Br has 1/2 cast into the underside of the mc. 1/2" = 12.7 mm

martin_csr wrote: The 81 650-CSR w single disk Fr Br has 1/2 cast into the underside of the mc. 1/2" = 12.7 mm

Thanks; I didn't know that. I changed my posting to eliminate the reference to 14mm. Ed

The aftermarket mc's I've seen are usually 12.5 mm, 14 mm or 16 mm. I think the 14 mm might be a single disk size or maybe either/or. ??? I haven't looked at the ones from usa-motorcycles-inc in a while.

Job done. It fits well, I actually have MORE feel than before and I managed to break my throttle tube while removing it to line everything up.

I think this swap was done in the past for looks or for a smaller looking area in front of the rider. For me, the original looks the part and as I have more feel, it's an added bonus.

5/8 by the way.

It's hard for me to believe that means 5/8 of an inch so what does it mean ...anybody know?

Although these are all 'metric' bikes, a few imperial measurements like ball bearing sizes, brake mc and tyre rims remain. The reason was economics, it was cheaper to source imperial sizes for some components .

I've spent a few days now with the new "old" MC and I cannot believe the difference. Night and day. The oem MC is light years better than the one I removed. Better feel, better stopping, better everything down to the way it looks on the bars. I'm just flabbergasted as to why it was replaced in the first place.