Locked Rear Brakes?

26 replies to this topic
  • MANIAC998

Posted July 18, 2002 - 05:26 PM


A buddy of mine has a 250F, and his rear brakes continue to lock up repeatedly. Now, it all started after a minor crash. He then noticed his reservoir hose had a leak, so in a pinch, he went to an Auto parts store and got fuel line, or something like that, and used that. Now, weeks go by, and all of a sudden, his brakes start locking up! Just yesterday, enough to cause them to catch on fire! I bled them for him once, and I had to blow compressed air thru the brake line first, just to get fluid to flow thru it. Something was blocking it. He says his fluid is black again. So we need TT'ers help. Do you guys think that the hose is "breaking down" and plugging up the brake line or what? I have never heard of that before, but this has me puzzled! Thanks for all of your help!! Maniac :)

  • Guest_Guest_*

Posted July 18, 2002 - 05:44 PM


He had bettr get that "FUEL"???? line off of there right now!!!
That brake fluid will eat right thru paint!
Dont you think it will eat thru fuel line like a hot hkr thru butter!
It is eating it away and the GOO is flowing thru the line into the cylinder!
You GOTSTA have BRAKE line!
Go to a Hardly shop and they may be able to put together a steelbraided one for about the same as the YAMMY stocker.
A brake shop will/should be able to put together a reg one for cheap. Those BANJO fittings are as common as MONICA LUINSKI was 2yrs ago!! :)

  • BigLou

Posted July 19, 2002 - 01:05 AM


The brake fluid is breaking down the line you have on there. It's possible that it is swelling it, causing the I.D. to shrink and effectively applying the rear brake very slowly. Eventually it locked up. The friction of the brake as it is partially applied because of this only exacerbates the problem. Had a buddy fill his front brake res to the top and after a couple miles in a scramble, his brake locked. He's sit for a few minutes until things cooled down, then take of again, only to repeat the process!

Get the right line and you should be good to go. :)

  • MANIAC998

Posted July 19, 2002 - 01:46 AM


Thumpin' Rock Hucker. I understand what you are saying, but, it is not the brake line, it is the short 3" reservoir hose. And it certainly was not the cost that made him put on the "fuel line". The Yamaha shop didn't have one in stock, and he wanted to ride so he thru this one on. Do you still think it is the root of all of his trouble? I have to admit, I'm begining to think so too. Damn shame that he just went and bought the complete rear brake assy. from someone parting theres out, when all he needs is the $2.00 hose!!! Thanks, Maniac :)

  • MANIAC998

Posted July 19, 2002 - 01:52 AM


BigLou. Thanks for your input. That helped me visualize what might actually be happening. At least its a good theory. He might have done some serious damage during the fire, so he went and purchased acarters complete assy. off of TT'ers. Hopefully they will come in in time for his next race. Again, thanks! Maniac :)

  • Guest_Guest_*

Posted July 19, 2002 - 06:02 AM


I still think the rubber is breaking down and clogging the whole thing up.
I had a freind that put "some kind" of line on his yz250 and it took only til' the end of the day b4 his bike shut down in the middle of NOWHERE!
Brake fluid is a lot harder on things (especially rubber) than even gasoline.
Put a drop of brake fluid on the back of your hand and dip your whole other hand in a jar of gasoline. Wait about 15 seconds and wipe them both off. Brake fluid is SO bad that close to 100% of the oil in your skin has been drawn out while the gas just "KINDA" dries skin out.
My point is that Brake fluid draws out petroleum and moisture frome ANYTHING.
I think even this short hose is made of a rubber that is designed for brake fluid.
If it were me, I would replace the hose with brake line, flush,flush,flush! :)
Go to an Automotive MX shop and they should have a piece laying around. They may even give it to you ! :D

I also think that BL has got part of it too.
That stuff will swell big time. Make sure he does not overfill the res! :D
Good luck and let us know how it goes. :D

[ July 19, 2002: Message edited by: THUMPIN' ROCK HUCKER ]


Posted July 19, 2002 - 06:37 AM



  • MANIAC998

Posted July 19, 2002 - 07:56 AM


Yes, I know. He was not trying to save money on a $1.50 part, the nearest Yamaha shop did not have one in stock, so he used what he could find. Does everyone agree that that hose is the problem? I never knew that brake fluid would do that to fuel line. Like I said, he has replaced everything now. I am only asking so as to have some more knowledge in my cranium! Thanks for the input. Maniac

  • acarter920

Posted July 19, 2002 - 09:27 PM


Ya know, come to think of it... that happened quite a bit with the brake line I sold him. I thought it was normal...

JUST KIDDING! haha... I had ya worried, didnt i?

Complete rear brake system will be in the mail for sure on Monday. He payed me, but I have been working and unable to get to the shipper before they closed. Email me to let me know when his next race is... I will try my best to make sure it is there for him by his next race...

  • txthumper

Posted July 19, 2002 - 09:55 PM


there is a little hole in the master cylinder..its a back bleed hole..if it clogs, which it does..take a little piece of wire..its got to be little..i use a piece of wire off an old cable..run the wire through the hole and , boom..nice brakes again!

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  • MANIAC998

Posted July 20, 2002 - 01:30 AM


TXthumper. Hey, thanks! I forgot all about that bleed hole. That probably is what is causing all of his problems. It wouldn't take much to clog that hole. Good advise! Maniac :)

  • MANIAC998

Posted July 20, 2002 - 01:34 AM


acarter920. Oh you funny guy you! Yes, you did have me going for a second or so. Curtis has a race on the 28th of July that he wants to go to, next Sunday. That should be doable, right? Thanks for helping him out. Maniac

  • Boit

Posted July 20, 2002 - 02:38 AM


txthumper....A good size wire for that is from the high "E" string of a guitar. I just clip off the left over piece near the tuner when I change strings and slip it into my tool box to replace the old one that is beginning to rust. The extra light gauge is a .10" diameter. This particular size wire is very handy for reaming out the slow jet in a Honda lawn mower.

[ July 20, 2002: Message edited by: Boit ]

  • acarter920

Posted July 20, 2002 - 03:59 PM


yeah, the 28th is definitely doable... I'll most likely get it out on Tuesday, and it should be there friday or saturday.

  • icemanyz250f

Posted July 24, 2002 - 12:50 PM


Hey Maniac, i replaced my reservoir hose with the one i bought from yamaha of troy. I rebleed my brakes and tryed it out. I got about 15 feet closer to Richs house and they locked up. So i dont know if that is what was causing them to lock up. Hopefully ill get my new brake assembly in the mail soon before sunday. On good thing, on the way home this time they didnt catch on fire. :)

  • seymourbutts

Posted July 24, 2002 - 03:16 PM


Had a problem like that. I had to rebuild the caliper to fix the problem.

  • sirthumpalot

Posted July 25, 2002 - 04:28 PM


Agreed, it sounds like the caliper is sticking somehow. Try as best you can to verify that it's not sticking. I wonder if the pins were bent in the crash... You can remove the pins and see if they're strait. If they're bent then I believe that can contribute to sticking brakes.

  • MANIAC998

Posted July 26, 2002 - 01:02 AM


Thanks for everyones help in this matter. Thats what makes ThumperTalk the best!!! Keep it up! Maniac

  • icemanyz250f

Posted July 26, 2002 - 03:11 AM


You got that for sure maniac, thumpertalk is deffentally the best. Thats one heck of a brake problem isnt it. Oh well at least my new assembly will be here soon. Hopefully today so i can get out and do some riding. Its no fun going to unadilla, coming home and not being able to ride.

  • John_Lorenz

Posted July 26, 2002 - 03:20 AM



Are you sure your buddies name is not MANIAC?

Never start a out a post I have a buddie that did

That means you did it :)

Hey this should be part of the superstition posts

Just razing ya

Once you get the new (BRAKE LINE) before bleeding, thuroughly clean the calipers, file or sand any burrs, round off the edge of the NEW pads

and apply just enough grease to the ears of the pads to keep things slipping

Then Bleed it real good..

[ July 26, 2002: Message edited by: E.G.O.**** ]

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