Do I need a Master Cylinder rebuild?

[NacsMXer]

I was just out in the garage trying to bleed my brakes. I was pumping the front brake lever when I noticed the rubber boot in the master cylinder started becoming wet with brake fluid. It's not grease that was on the boot before, it's brake fluid. I've never seen this happen before when bleeding the brakes.

Is this out of the ordinary? Does this mean I need a master cylinder rebuild kit? Thanks for your help!

http://img59.imageshack.us/img59/8329/dsc0774dc.jpg (http://img59.imageshack.us/i/dsc0774dc.jpg/)

http://img706.imageshack.us/img706/9133/dsc0775f.jpg (http://img706.imageshack.us/i/dsc0775f.jpg/)

[trailrider894]

Can't answer your question, but maybe this will help. My boot is a little torn up and no fluid is coming out, so i would say that a seal or something needs replaced.

[CJM]

Possibility.

What I would do is leave it alone for a few hours or a day, then come back and check the fluid level for it leaking as well as when you pump the lever.

I had a similar thing happen on a rebuilt rear caliper. It would leak into the parking brake block off after it sat-when you bled it-it was fine.

If it leaks anymore it probably needs seals. Looking at the diagram on the parts fiche, it shows #12 is a full kit where it replaces the seals and such-its also 40 bucks :( Might score a used one for 10 off ebay.

[supertrooper90]

jets r us sells master cylinder rebuild kits for like 20 bucks in case you decide to go that route

[NacsMXer]

Ok thanks for the input. You could see the part of the brake lever that pushes on the piston becoming wet as well and i've never seen that happen before. I just don't want to go through all the trouble of bleeding the brakes to get them perfect and then have a stupid seal let air into the system.

I priced out a new Honda rebuild kit and the list price is $36.58. I also need a new diaphragm, the black rubber piece under the master cyl cap, which is another $8.35. So that's almost 45 bucks there.

I can get a brand new master cylinder assembly with everything I need for $76.31. If I get it through service honda, it's $57.50.

For the price of the rebuild kit I almost want to just go 15 bucks more for a brand new assembly from Honda.

[Wheelie]

Why not upgrade to R brakes?

[NacsMXer]

Originally posted by Wheelie
Why not upgrade to R brakes?

The 450R master cylinder?

[togup]

What does the 450 have thats better?

[togup]

That doesnt look like its leaking enough to hurt

[honda400ex2003]

dual piston calipers on the 450s in front as far as i know.

if it was me, id just get a new one either way.

steve

[Nac's22]

If it is only a $15 difference I would just buy the new one to have everything new. but thats just me. :D

[bkb88]

If you are replacing the 400ex master I would suggest getting a nice used 450r master cylinder. The brake lever in my opinion has a much better feel and is also adjustable, comes with a lever boot (to my knowledge all first gen. 400ex's did not come with one from the factory), and also comes with a brake light switch. I have done this swap due to the same reason as you and it was worth every penny.

[NacsMXer]

I ended up going with a brand new 400EX master cyl shipped to my door for $67. All new stuff that I need anyway just bolt on and go like Nac's22 said.

I would have gone with the 450R master but it was like 85-100 dollars before shipping, it has a brake switch that I don't need, and I don't think my ASV front brake lever for the 400EX would have fit. If I didn't already have the lever I probably would have gone with it.

I'm trying to get twin piston YFZ calipers up and running, so it should be a nice upgrade over what I had before 450R master or not.