Master cylinder plunger

[dbeardslee]

So my brother asked me to do a bunch of work on his G, and I decided to start with the brakes. I rebuilt both front calipers as well as the master cylinder, but as it's been a few years since I wrenched on an XS, I completely forgot about that darn plunger seal's habit of popping itself off if you squeeze the handle too far while bleeding. I got paranoid about the very same thing low those many years ago when I rebuilt the MC on Betsy, and I took it back apart only to find it still in place. I'm trying to keep from repeating that episode.

At this point I've power bled the system, and I'm not seeing any air at the calipers. I can straddle it and roll it forward and when I hit the brake it grabs well enough to make the forks nose-dive. That's about all I can do to test it right now since it's not running yet. Seemed prudent to make sure it could stop before I made sure it could go. Problem is, it doesn't feel quite as firm at the handle as the front brake on Betsy. I'm thinkin' it wouldn't be grabbing at all if the plunger seal was dislodged, and maybe it just feels a bit different 'cause everything is new. Or maybe it just needs a little time for any air trapped in the lines to bubble its way to the top.

So what say you XSers - am I just being paranoid (again), or could that seal be out of place?

[3Phase]

Nope, you're not being paranoid.

If you even suspect that cup flipped over in the master cylinder just take it apart now and check it or you'll be asking yourself, "What if..." until the cows come home and you won't be able to have as much fun when you're out riding it.

.

[bikerphil]

Tie back the lever and let it sit overnight, that always helps to firm up the feel, it will get rid of any remaining air.

[DiverRay]

Stainless or rubber lines? That is #1 with me, as I have bikes with each, and what a difference between the two!
But first, +1 on bikerphil's comment. Allow the small bubbles to slowly work out of the system.

[dbeardslee]

This bike's got stainless lines and Betsy's got rubber. Phil's idea sounded like a good one to me too, and I tied the brake handle back last night. Seems to have done the trick. I can see that the fluid level in the reservoir dropped slightly, no leaks and the handle is WAY firm now. Must have just been a little trapped air.

Thanks for the tip, Phil. I'm moving on to the rear caliper and MC next, so I'll keep that in mind if it winds up feeling spongy.

Ray, I never even thought about those stainless lines, but your right - now that the air is out I can definitely feel a difference. I'm thinkin' Betsy's gonna want a set when I get through with my brother's bike. Where's the best place to get 'em these days?

[MPittma100]

Ss lines

Go to the product evaluations heading on the forum page for the brake line sources.