Yamaha R1 Forum: YZF-R1 Forums banner
1 - 2 of 2 Posts

· Bald headed dork
4,113 Posts
Discussion Starter · #1 ·
Recently I took my rear brake pads out and cleaned the caliper up. I put a small piece of wood in the caliper and pressed the brake lever to expose a bit more of the piston so I could give them a good cleaning as well. Both pistons looked fine, so I wiped them off and then pressed them back into the caliper. I finished cleaning the caliper and pads and put everything back together. I was mindful of the rear master cylinder. It dropped when pistons were a little more exposed than normal (which is to be expected) and rose when I pused them back into the caliper. However, when I went to put the diphragm back in, I had to take a little bit of fluid out so it would fit. It displaced a bit of fluid as I set it in the MC. After taking a little bit out, I put the diaphragm in the MC and put the cap back on. The brakes work just fine. In fact, I think they actually work a little better. When the bike is on the rear stand they don't seem to drag hardly at all.

So..........my questions are:
1. Why did this happen, i.e. what could cause the diphragm not to fit without displacing some fluid?
2. What exactly does the diaphragm do anyway? Do I even need it in the MC? I've seen some guys' bikes and they just have some tubing with a small cap on it instead of a regular MC. They obviously have no diaphragm, just some tubing.
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.