| Author | Message | ||
     Essmjay |
I lost pressure in my S2 front brakes on my ride up the mountain a couple weeks ago. Since then I have inspected the front caliper, replaced the pads, and rebuilt the master cylinder. The master cylinder parts looked fine, but I had a rebuild kit on the shelf so I went ahead and replaced the parts. The front brake line is braided steel. The pads were worn at an angle with more wear on the outer edge than the inner edge, but there was still plenty of pad left, There was no sign of stuck pistons in the caliper and no leakage. The relief valve on the master cylinder was spurting as it should. After putting everything back together I was unable to get the brakes bled. I also had no spurting on the relief port in the master cylinder. Suspecting the valve was backwards installed I took the mc apart and double checked the parts install. All was correct. Now I have tried mityvac, Henricks syringe method, also pumping into a container from the caliper, leaving the brake pedal squeezed overnight (even more than one night), every method I have ever used to bleed brakes. I can get just enough pressure to barely move the pads, but it just won't pump up past that. What am I missing? | ||
| Ratbuell |
Rebuild the caliper with new seals and pistons. I did it a couple years ago on my S2 and it made a HUGE difference. http://www.americansportbike.com/shoponline/ccp0-p rodshow/17085.html for the seals for the rebuild; I think I got my piston set from PM. Either that or 44148-94Y from the dealer had pistons in it. I forget. | ||
| F_skinner |
Sounds like seals like Joe said... I doubt you will need new pistons... http://www.americansportbike.com/shoponline/ccp0-p rodshow/17085.html Frank | ||
| F_skinner |
One other thing. I have not had a problem bleeding the front brake on any S2 but did have a problem with the S1W.. RT told me to elevate the brake above the master cylinder and it worked like a charm. Good luck Shane | ||
| Essmjay |
I will go ahead and rebuild, but it seems that will only fix the uneven wear. Looking at the blow up of the caliper parts, it seems that if the seals were leaking I would have fluid coming out past the piston, and that would cause a loss of pressure. The pressure loss was pretty dramatic, I had good brakes when I started the ride, by the time I was back home the same day I had no front brake at all. There is no leakage visible anywhere on the system. Is it possible for fluid to leak past the piston seals and yet still stay within the system? | ||
| Ratbuell |
Not really...but it *is* possible for there to be a blockage in the caliper, keeping fluid from the line from even getting to the pistons. Unhook both ends of your line, and blow it out good with compressed air. Then test flow by blowing through it with your mouth. Could be a piece of old seal debris, or just plain ol' Old Age Gak, stuck in there preventing fluid flow. | ||
| Fireball7709 |
Old Age Gak always seems to be my problem! Oops, you were talking about brakes  | ||
| F_skinner |
Shane, any progress? I am curious to hear what you found out. Frank | ||
| Essmjay |
Frank- Not really. I have replaced the seals in the caliper, blown out the brake line, gone through the master cylinder again, and still no real progress. I have been pumping fluid back and forth with a big syringe, also mityvac and gravity methods. I am getting no air bubbles now, but still no real pressure. The one thing I find odd- you know how if you have the lid off the MC and pump the brake you will get a spurt of fluid from the pressure relief when you release the handle? When I initially opened the system I had that, but not since I rebuilt the MC. That is why I took the MC apart two more times, thinking I might have installed the parts backwards and to ensure all the ports were clear. Maybe I just don't have enough pressure in the system to make it need relief? Anyway, frustrated and no time to ride this weekend and no time to work on it, so right now I have the brake handle clamped closed and hoping some hidden bubble will rise to the surface. Shane | ||
| F_skinner |
I have no ideas... | ||
| Road_thing |
When I did mine, the sealing washers on the banjo bolts were leaking. Make sure yours are good. rt | ||
| Essmjay |
That is a good point rt. I have had the lower banjo off enough times the last week that the rubber on the washers could be toast. Anyone know if the washers are a standard size I can pick up at auto parts stores, or other bike dealers? sj | ||
| Jayvee |
Yah, standard, I'm using some cheap copper washers from Harbor Freight. Works great, no leak. | ||
| Essmjay |
Update- I have hit a brick wall on this. My next step is to replace the master cylinder. The Buell part# is 45019-93, which is off a '93 FXR with a 5/8 bore. Price for that part is around $200. I have found a NIB 45019-85A which is for a '92 Sportster and has a 5/8 bore. It is on fleabay so I may or may not be able to get it. Do you guys think it will fit? Shane | ||
| Essmjay |
I was also looking at #45146-04, which is a '04-'06 1/2" bore for sportsters. I could get that one for $60 right now. I seem to recall that going down in bore size is ok, but increasing bore size is a negative? |
