After I bleed my brakes they work just fine for an entire day but go soft after another day or so. I've never had issues on track, I just bleed the master in the morning. After a couple weeks of sitting the brakes will completely go out but after a quick burp of air out of the master and they work fine. Is my master cylinder going bad or do I have a leak somewhere that is letting air in? Im using the stock nissin on my Daytona 675.
My SV was doing the same thing at my last round of racing, except it didn't even last a whole day. I think it's the master, so I plan to rebuild it and the calipers (for good measure) this winter.
No external leaks noted? You're bleeding directly on the master by a bleeder? If you are actually trying to diagnose, I'd probably rebuild calipers first, replace crush all the crush washers at that time as well and see if your problem is still there. If so I'd suspect the master.
You can pop the dust seal off the plunger and see if there is any leakage present. If any at all, rebuild it. It's a simple piston system with some seals, so it should either be leaking or not. Not much else to it. Only other thing I've heard about introducing air without a leak of some sort, is chemical reactions (corrosion & moisture presence in system), but that takes a good amount of time to occur. When you bleed the master, do you see any red mist (rust) in the fluid?
Nope, no leaks. I've been bleeding from the master, that's where I always get some air out. I'll probably just replace it just to be safe. I'll take a look at the calipers too.
