Rode GNF at Barber bike was fine in dry Thursday practice. Friday morning practice in pouring rain, lever felt spongy so I adjusted it and raced. It was worse during race but manageable. Got home and unloaded lever goes all the way to bar. No leaks are present. Yall ever heard of anything like this?
Possibility you boiled the fluid in the caliper, that created bubbles, and those bubbles have floated up into the master cylinder, as the bike sat. First thing I’d do is fill a baster or large syringe with brake fluid and try pushing fluid up through the system. The bubbles should come right up into the reservoir. If that doesn’t get it, I’d try a vacuum pump and see if you can pull the air through the system. Not sure what you’re using for fluid, but, I’d suggest Motul RBF600 or Motorex 5.1.
Yep. Higher boiling points on both those products. R3 is an entry-level bike and was never designed for competition use. That single caliper absorbs a lot of heat, transferring it to the fluid. I’m not sure how you wouldn’t think the quality of the fluid would have anything to do with it.
I get those fluids have a higher boiling point but have a hard time believing the DOT fluid would be boiling in wet weather.
If he boiled the fluid the first day and those bubbles floated to the master overnight, things will only continue to worsen, as he continues to ride it. If he’s on the original fluid, it’s an even worse situation.
Oh forgot to say, it was Motul RBF 600 fluid from a bottle that was previously opened. . I will buy a new bottle and change the fluid
And I rode it once at RRR. plus open Friday practice. Two rounds at Road A plus a Friday practice then Barber. Guess it was due. Trying to learn this little bike
That stuff is incredibly hygroscopic. You really need to flush it, before each event. I left it in a previous bike over a winter and had white sludge-like material in the bottom of the reservoirs, the next spring. I don’t believe it’s good to use RBF600 out of any opened bottle that’s more than a couple months old. I switched to Motorex 5.1 and have yet to experience anything like it, since.
Still need to flush the Motorex before every event, just like a pro team’s regular maintenance schedule. It’s cheap insurance to be safe, man.
Cheap insurance @ $22 pint vs $3 for regular DOT4?? What exactly are you insuring?? So the OP has been using $22/pint fluid... now what??? lol If you change the fluid at every event... whats the benefit to the high dollar stuff vs standard fresh DOT4 if you are using the proper pads for your pace???
Some good/fresh fluid never hurts, but RBF fluid once/season has been just fine for me on the R3. You don't really need to use the brakes much on the R3... A couple other things to do though: Clean the brake caliper piston(s) really well. Extend them out a little and then clean. Sticking pistons can cause some extra lever play in the lever. Also are you using an aftermarket lever and or recently changed levers? We had a problem on one R3 with a particular brand of lever (can't remember the brand right now, sorry) that wouldn't allow for the right amount of travel and I think that made brake bleeding less than successful. Also triple check for leaks, especially if you have the rubber lines still. Doesn't take much air at all to ruin lever feel. Carefully look the whole length of the lines, all the fittings, in the piston area of the caliper and master, and the bleed fittings. Brake pads have enough meat left on them? They last so long on the R3, but do eventually wear out. It's possible it's still the brake fluid, but not the only possible cause. Give the whole system a thorough once over to make sure you've got a good brake system.
I just crash and the clips ons usually go flying along with everything attached to them. It's like a car that burns oil, you never really have to change it, just keep adding..
