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Discussion Starter · #1 ·
so, my next problem i guess are my brakes. I had them professionally bled, and they were great for about a week. now, they are getting soft all over again. I went back and asked him, and he said it could be an o ring or a pin hole in the brake lines. I just put a new rear caliper and break pads in the front and back. so, how can i diagnose this issue? thanks for the help.
 

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Something I would try is take a heavy rubber band, a velcro strip, or even a belt. Pull the brake handle and use whatever you can to hold the brakes on. Leave it on overnight and see if that helps.
 

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I understand it opens the valving by the master cylinder, allowing any air in the lines to escape to the reservoir.

Even holding the brake lever for a few seconds helps.
 

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Jim answered why to try it and if that don't help we'll need to try something else. I don't like to think pessimistic I would rather be optimistic and think it will work. Now after it has sat overnight I would look at all the brake lines and at banjo and other fittings to see if you can see if any are leaking. I have seen air get caught by the master cylinder and the banjo fitting and have to crack the bolt holding the banjo fitting on while holding pressure on the brake handle. Good luck and let us know how it works out.
 

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Discussion Starter · #7 ·
Well, I tried it for a day and a half straight. It has only gotten worse. I had the whole front off and didn't see any leaks. How is air getting in the system?
 

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Most likely trapped in the banjo fitting.
Not a fun thing to get rid of either.
 

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Discussion Starter · #10 ·
Well, I tried gravity bleeding them, and I was told all that did was add more air. I had them suction bled just 2 weeks ago. Could an o ring be bad in the caliper?
 

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Have you tried to bleed the banjo bolt while holding pressure on the brake handle ?
 

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Discussion Starter · #12 ·
I'm not sure what you mean. I just crack open the bleeder bolt. My mechanic thinks that the O rings in the break handle have rotted away because someone put dot 3 not 4
 

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Hmmmm not sure how that would happen. The difference between DOT3 and DOT4 is that DOT4 has a higher boiling point. They're the same compounds (glycols). DOT5 is the one that's incompatible with everything else (silicones instead of glycols).

If it were my bike, I'd start with the easy stuff first: bleed 'em again. You'll want a helper (to pour fluid into the reservoir and to squeeze the brake handle). I haven't done my 650's brakes yet but my rule when doing my 4-wheelers is to always close the bleeder valve while someone has pressure on the brake pedal and fluid is squirting out of the bleeder. Otherwise an air bubble can enter the caliper via the bleeder valve. Buy enough DOT4 to run several reservoirs of fluid all the way through the system and out. After you get the timing down with your helper, have her squeeze really hard a few times to try to dislodge any bubbles that may be "stuck" in the system. Remember to close the bleeder when pressure is still on the brake handle, i.e. you want to stop the handle from moving by closing the bleeder. Never take pressure off the brake handle or allow it to bottom out, air will enter the bleeder for sure. Also, never allow the reservoir to become nearly empty or it'll suck in air when your helper releases the handle.
 

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I'm not sure what you mean. I just crack open the bleeder bolt. My mechanic thinks that the O rings in the break handle have rotted away because someone put dot 3 not 4
What I mean is just what I said. You need to hold pressure on the brake handle and at the same time crack open the bolt holding the banjo to the master cylinder just long enough to let any air out. Make sure you tighten the bolt before you let the handle back out.
As Mike said dot 3 & 4 are compatible, so no problem there. And he also gave good directions how to bleed the lines. Let us know how you make out after you have tried these two things. :wave:
 

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If you hold the lever in with a rubber band, and you have a leak, you will find the lever all the way to the hand grip in the morning. You may or may not find leakage, because sometimes brake master cylinders leak internally - past the piston seals. If this happens to you - time for a rebuild of the master cylinder....
 

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Discussion Starter · #16 ·
well, what seemed to be the problem, was that the bolt that held the lever wasn't quite right. So, I swapped it out with the right one, and it did help some. I think there is still a little air in there, but it stops much better now.
 
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