What's up? Just wanted to see if any of you guys had swapped your stock front brake master cylinder for a cylinder from another year, or make? I ask only because I am having a re-occuring problem with air getting into my lines up front and I have checked all summer for the leak on the pressure side of things and there is none. So that leaves the seals in the master, and I have had no luck finding a rebuild kit. I've been thinking on whether or not other models (1000RR) maybe had a larger piston in the master that would increase my brakes power. If I am getting a new cylinder I might as well upgrade. If anyone has any advice on the issue or whether I should just stick with a stock replacement let me know.

 

Well, I thought my cylinder seal had gone hard also, but it was actually sucking air around the bleeder screw on both calipers, even though the screw tips look new, and were as tight as I dared. Very slight, but still noticeable bubbles. A little teflon tape around the threads fixed the issue...so far. But it requires new tape for every fluid change. I highly recommend new steel lines if you have not already. If you are still on OEM rubber...holy moly change them.

I would be interested to know if anyone has an upgraded master...although mine is original and still working after a manufacture date of Feb 92, so I'm going to go knock on some wood.

 

really...interesting. How were you able to confirm the leak, because I would think that the pressure generated in the lines and system would cause a visible leak of fluid anywhere there was an air leak. Like you my bleeders are in new condition and I tighten them as you do, very tight. I do have stainless lines so I have been pissed that air keeps getting in there and ruining my lever feel. Also, when i worked as a mechanic my boss told me not to use teflon tape on brake lines, but I think that was because it could dislodge and clog the ABS system, which our bikes do not have. Maybe speed bleeders would help, as they do not have to be screwed and unscrewed. I will try the teflon tape when I bleed my lines in a few weeks.

 

I could see bubbles continue to rise, even with the screws tight. At first I assumed it was just air from the empty lines, but after an entire bottle...I knew it had to be getting sucked in from the outside, whenever I squeezed the hand pump. That's when I started blaming the master seal...but in the instructions for the Mity-vac, under "motorcycle brake-bleeding troubleshooting", it recommended wrapping the threads with teflon tape. So I went with it, even after reading elsewhere, like you, that teflon and brake fluid should not be combined. After that I could see no bubbles and pressure maintained itself constantly.

As far as the air leak not producing fluid around the screw beforehand...I don't know. But there was no fluid that I could see or touch. I have always thought that a pressurized fluid system actually draws air in, in small amounts, rather than allowing fluid to leak...up to whatever point causes the pressure to drop. But I have not confirmed it.

 

thanks for the info my friend. Very helpful and basically the exact same thing I have dealt with. I went through an entire bottle this summer and I was going a little nuts. The Teflon should be no big deal, the worst that could happen is it somehow clogs a line fitting. I will definitely take your advice when I do my post season cleaning and maintenance. Be good