RT front brake master cylinder

[outpost22]

My '96 RT front brake master cylinder is leaking small drips onto the tupperware. My dealer is ordering a rebuild kit for it.

Now to my question(s).

He suggested that I can rebuild it leaving it in place on the bike, or disconnect the heated grips (remove tupperware to get to the wiring) remove the MC and do the rebuild off of the bike.

 

Who has done this rebuild, and what method did you use?

How long did the job take?

 

Thanks

[smiller]

I left the master cylinder in place on the bike for my rebuild and had no difficulty in doing so... there's plenty of room to work. The only reason I could see for wanting to remove it is if the bore was severely corroded and needed a lot of work, but in that case I'd probably just replace the whole thing.

 

It's a relatively easy job, just remove the retaining screw on the side of the MC, remove the piston and spring, clean out the bore as required (flush everything out well with alcohol or brake fluid afterwards if you decide to recondition the bore) and reassemble. Bleeding everything afterwards is probably more of a pain than the rebuild work itself.

[outpost22]

Thanks Smiller

 

Now, I guess the next question would be what is manageable corrosion, and what is not fixable. I have not removed the MC yet, so perhaps if I can get a photo of it, we could do a poll as to whats salvageable

[smiller]

What you're probably going to find is a buildup of crud (dried brake fluid) at the very end of the bore which is what eventually causes the seal to fail and start leaking. You can usually clean it up with some fine (400 grit or so) wet sandpaper and you'll be good to go. Again, flush everything out well before reassembly.

 

BTW, you can prevent this from recurring by removing the brake lever and rubber boot every once in while and cleaning everything out. This won't require bleeding anything and is easy preventative maintenance.

[CRAIGO]

I rebuilt mine in the Spring. Leave it on the bike. Disassembly, cleaning and reassembly can be done in an hour. Just make sure you don't clean it with anything real abrasive that will scratch the bore.

[Ken H.]

I've rebuilt them, usually remove them though. Easier to work on, clean up, inspect, flush out.

 

I use a dremel and a polishing wheel to shine the bore back up. Then flush it out well with new fluid before reassembly with the rebuild kit.

[exwingnut]

I've rebuilt them, usually remove them though. Easier to work on, clean up, inspect, flush out.

 

I use a dremel and a polishing wheel to shine the bore back up. Then flush it out well with new fluid before reassembly with the rebuild kit.

 

Do you use a hone to remove any wear before you polish the bore?

[smiller]

Do you use a hone to remove any wear before you polish the bore?

I don't think that's necessary in most cases, you'd probably do more harm than good (or at least I would. )

[Ken H.]

Do you use a hone to remove any wear before you polish the bore?

No. If it's pitted to the point where it needs to be honed and a simple polishing compound won't get it back, time to replace. Very few I've seen are that far gone though.

[outpost22]

Update.

Got the rebuild kit today. Everything was fairly straight forward. I had virtually no pitting inside the bore, and the only gunk accumulation was on the tip of the piston/rubber boot, where the fluid has been dripping.

Took #600 sand papaer to the bore lightly, flushed with brake fluid, and blew it out with compressed air.

The only major screw-up (so far) is that I didn't position the brake light switch lever correctly and had to do some disassembly to get that corrected. Other than that, bled the brakes and the brake lever seems real firm. Will test tomorrow as its supposed to be 99 degrees this p.m.

I'm not THAT ambitious to go riding in it.

Thanks for all your help. Now we'll see if it holds the fluid.

[smiller]

I had virtually no pitting inside the bore, and the only gunk accumulation was on the tip of the piston/rubber boot, where the fluid has been dripping.

As always.

 

The only major screw-up (so far) is that I didn't position the brake light switch lever correctly and had to do some disassembly to get that corrected.

As always.

 

Sorry, guess we should have warned you about that one...