Master cylinder rebuild kit part #?

[shpielers]

Hey guys. 2006 Kat 600.
My brakes haven't been all that great lately. I replaced the stock lines to G&J SS lines a while back. That helped a bit, but sponginess never went completely away and has started getting worse. I've bled at the calipers a ton, and at the MC. Reverse bled, zip tie the lever over night, normal bleeding, rinse, repeat,repeat,repeat...Bleeding usually nets 1 large bubble and some teeny tiny ones on the first go, nothing after. It firms things up a bit for maybe 2 days before getting spongy again. Methinks something isn't right if that sponginess keeps reappearing. I don't see any fluid leaking from anywhere, and the pads seem to float ok on their pins. So I figured I'm just going to clean/rebuild everything. Bike has 57k miles on it and I've done 51k of those. Aside from putting on the SS lines, the front brake system has only ever received TLC in the form of flushing/bleeding (2x per year). Worst case scenario it won't hurt anything.

I found rebuild kits for the calipers easily enough, but am having issues with the MC rebuild kit. Looking at the fiches on ronayers and bikebandit, it seems like the 03-06s don't have exactly the same parts as the 98-02. I can find kits for '02 and earlier, but not for 03 or after.
Does anyone know if the master cylinders did actually change, and where I could actually find a kit? Or if it's all the same and the 02 and earlier will work fine? And/or am I just an idiot and just looking at the fiche wrong?

Also, if anyone thinks my issue might be caused by something else that a rebuild won't address, please chime in.
Cheers!

[shpielers]

Forgot to mention: The SS lines I put on were the 2 line set up, so it's not air getting trapped at the splitter, or something there not being tightened down enough. Also, I have 3 times checked all bolts were torqued properly. I used the new crush washers provided with the SS lines when installing.

[mammut89]

I put my money on a couple of things , they could all be going on and adding up to the problem, I doubt the problem is in the master cylinder.

1. Grooved pad slider pins.
take a flush metal file and go over them , you will immediately see the areas that do not become shiny, thats obviouly the pitting. Dont use sand paper. Sand paper will take away the dirt but wont make the pin straight. If they are really bad just replace them.

2. Unevenly worn brake pads.
They will sometimes make the caliper piston not move straight and will get hung up causing a gap that will in turn make the lever move too much.

3. Caliper needs service.
If youve got the original seals and caliper pistons Id just service the calipers and be done with it. The pistons get pitted and a small pit that doesnt look too bad can cause the piston to not retract properly and might cause air to get sucked in on the return.

4. Last but not least the good old air pocket. Ive had good luck with taking a small c-clamp and pressing the brake pads completely in so that there is no room on the back of the caliper pistons for air to get trapped. Once they are pressed completely in you can start bleeding, it has helped me.

leave the master cylinder alone untill all of these things have been tried first is my 2 cents

[shpielers]

Thanks mammut! I saw the c clamp trick mentioned in a thread when I was doing some research the other night, definitely going to give it a try. And your point 3 about the pitting on the pistons drawing in air sounds like a likely culprit. I ordered caliper kits last night so next weekend I'll be diving in. Hope I don't need new pistons... I've looked at the pin and pads on the bike, seem ok, but once I have everything off I'll be giving them a much closer inspection.
Thanks again!

[shpielers]

So the pins are grooved pretty bad, not sure how i thought they were ok. Replacing the tiny pin is easy - for the carrier assemblies, whose pins both have grooves, can those get filed down, or does the whole carrier need replacing?

[mammut89]

I think that needs replacing

[shpielers]

Dang. Kinda what I was expecting, just wanted to make sure first. Looks like that 5* advance is going to have to wait a while longer....

[shpielers]

Got all the parts in, WAY better. Now my brakes are nice and firm. New carriers, pins, pistons, seals, and master cylinder rebuilt. Finally getting the full benifit of my SS lines. .
For anyone else confused by the parts diagram and looking for a MC rebuild kit, you only need part #2, #3 is included in it and does not need to be separately ordered.

http://www.bikebandit.com/2006-suzuki-katana-600-gsx600f/o/m9761#sch510897

[rschlegel]

Congrats on getting it take care of!