Front brake loses play

[LazySatyr]

This is the weirdest brake issue i have ever had. At rest my front brake is normal, little play but not soft. However after riding about 5 mins the play will gradually disappear until even the slightest pressure on the master cylinder lever causes medium to strong braking. I first tried lowering the level of fluid and the replacing the fluid entirely but neither has affected the issue.

Does anyone have any idea what might be happening here?

2005 XB9R

 

[Cooter]

First off. Have you just changed the levers? The wrong/cheap ones can do that by pre-loading the master cylinder plunger.

If not, look in the master cylinder. There are 2 holes in the bottom, a large one and a VERY small one. If the small one is clogged it will do that.
Stick a piece of stainless steel (you can pull out one from your BBQ brush), welding tip cleaner, or jewelers drill through it. It's OK to do with the master assembled.

No matter what, FIX IT NOW. The next step is, it will lock up the front brake, and that is no bueno…..

 

[LazySatyr]

Thanks cooter, yeah i figured this would get very bad if i didn't fix it, i think it may well be the small hole as when i was bleeding brakes no air came up the way you'll often see a few bubbles do.

I'll clean that now and let you know if it works!

 

[LazySatyr]

Well i took some fine gauge wire and poked around in there but had a difficult time with the hole being as small as it is. Seem to bring up one little piece of crud out but when i went for a quick ride the problem persisted. I'm considering swapping out the master cylinder for a new one, are there any requirements for a master cylinder on the XBs?

 

[user_deleted]

these are incredibly simple nissin brake systems and your problem will be caused by 1 or more of the following so check them all:
1-bleed return hole in m/c clogged as cooter stated
2-one or more caliper pistons stuck in its respective bore.
3-collapsed brake hose.
4-pads hung up on caliper slide pin causing 1 or both to rest firmly on rotor generating heat as soon as you ride.

 

[LazySatyr]

I managed to clear out the return hole and bingo brake are perfect again. Thanks everyone.

 

[thrstrmech]

next time around in bleeding the brakes, try reverse bleeding...caliper to res, you'll get all the air out and possibly anything clogging the line.

glad you got it worked out...now go ride it like you stole it

 

[LazySatyr]

So my brake issue has returned. The weird thing is now as i ride the play on the lever will increase and then decrease, as if something clogging the return hole is moving in and out of the way (that's a total guess).

It freaked me out while riding the bike yesterday

 

[LazySatyr]

It also only occurs when riding, at rest the brake play remains constant regardless of temp or me pumping the lever for a while

 

[nicholas900]

Does the front wheel spin free with wheel off the ground? Lunitic pretty much nailed all the options.

If you pump the brake and the wheel spins free, then I would think that would eliminate sticking pistons or pads on the pin or on the caliper. So if it spins free I would say your problem is in your master. I'd start with this.

Although this has never happened to me, I've heard of it often. It usually results in unintentionally locking up the front wheel while applying light brake effort and a wipe out.

 

[LazySatyr]

Ok, did a longer ride today, brake lever play stayed about the same as far as i could tell but i'm not saying the problem has magic'd itself away.

Front wheel seems to spin fine with no resistance when i push the bike in neutral, i did however noticed the inside brake pad can be wiggled with a little pressure, sort of around a central pivot. I'm guessing it's loose and is sometimes rubbing cause my issue and the releasing, relieving the issue.

does this sound right?