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Brakes locked Up...Again


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Last Wednesday and Thursday on the way home from my rear brakes locked up on me. I had a 8mm wrench that I used to release the pressure. I was surprised to see steam coming out of the bleeder valve. I pumped the brake until fluid came out. This released the pressure enough to get me home. Friday before going to work I bled the rear brakes then rode to and from work with no issues thinking all was good now. This happened to me a month or so ago but I thought it was water in the fluid or just over filling it and bleeding them seemed to work.

 

So Saturday my daughter asked if she could use my bike to get to work and since I can’t ride for a week (had recent surgery to remove a basal cell carcinoma from my forehead) I let her take it. I warned her about the possibility of the brakes locking up and what to do if they do. Well they locked up on her. She handled the bike just fine and got off to the side of the road. She got off the bike proceeded to take the right bag off and a Highway Patrol officer pulled up offered to help but had no real knowledge for these bikes so he just turned his lights on and positioned his vehicle to help protect her from traffic. (I would like to say thanks to that officer) She got the bag off (she noticed that it was melting and actually bubbling where it was closest to the brake caliper) released the pressure and was able to continue on to work.

 

 

I am also thinking that I may need to replace my rear brake pads (probably glazed from the heat)

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On cleaning out the expansion hole the wire from a twist tie will generally get the job done. On the steam coming out of the bleader valve, that is water vapor and the brake fluid needs to be completely flushed from the line and caliper. Do yourself a favor and pick up a set of Speed-Bleeders for the calipers and the clutch slave. The rear caliper will get hot enough to melt the abs plastic of the saddle bag. What might have happened is the master cylinder cup may have been damaged by the heat, and you're not getting a good seal on the cylinder walls.

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I did get the Speed-Bleeder the last time the brake locked up on me. I was actually using the twisty tie wire (got the idea from a prviouse post of yours) to try and clear that hole but the buildup extremely hard for some reason. I ended up using a pin from my wife sowing kit to brake it up then finished it with the twisty tie.

 

 

I have a second MC that is also hanging up ( Maybe I just put them back togeather wrong :doh:)

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I did get the Speed-Bleeder the last time the brake locked up on me. I was actually using the twisty tie wire (got the idea from a prviouse post of yours) to try and clear that hole but the buildup extremely hard for some reason. I ended up using a pin from my wife sowing kit to brake it up then finished it with the twisty tie.

 

 

I have a second MC that is also hanging up ( Maybe I just put them back togeather wrong :doh:)

 

One other area that can cause repeated lock ups is a reserve that is too full. Not saying, but it might be worth a look. I had rear lock ups with my '83 when I first bought it. Brake would lock up tighter than a frog's a$$. Rebuilt the whole system, and it turned out to be a plugged expansion hole. If you have a lot of residule crystals in the lines this could cause the thing to be plugged repeatedly. I blew out all the lines... rag over one end... with compressed air to clean them out.. Clutch lines too...

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I will have to try that tonight. There did seem to be some buildup in the hose from the reserve. I can't tell if the reserve is too full or not. I just fill it until it starts to come out then suck out an ounce or two with the syringe.

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Last Wednesday and Thursday on the way home from my rear brakes locked up on me. I had a 8mm wrench that I used to release the pressure. I was surprised to see steam coming out of the bleeder valve. I pumped the brake until fluid came out. This released the pressure enough to get me home. Friday before going to work I bled the rear brakes then rode to and from work with no issues thinking all was good now. This happened to me a month or so ago but I thought it was water in the fluid or just over filling it and bleeding them seemed to work.

 

So Saturday my daughter asked if she could use my bike to get to work and since I can’t ride for a week (had recent surgery to remove a basal cell carcinoma from my forehead) I let her take it. I warned her about the possibility of the brakes locking up and what to do if they do. Well they locked up on her. She handled the bike just fine and got off to the side of the road. She got off the bike proceeded to take the right bag off and a Highway Patrol officer pulled up offered to help but had no real knowledge for these bikes so he just turned his lights on and positioned his vehicle to help protect her from traffic. (I would like to say thanks to that officer) She got the bag off (she noticed that it was melting and actually bubbling where it was closest to the brake caliper) released the pressure and was able to continue on to work.

 

 

I am also thinking that I may need to replace my rear brake pads (probably glazed from the heat)

Your brakes should NEVER get that hot under normal riding (heavy mountain riding or junior road racing, maybe, but not normal service). The reason they are heating up so bad is because they are dragging. And they are dragging for the same reason they eventually lock up - something is wrong with your hydraulic system to prevent the fluid from moving normally back into the master cylinder. Unless there is something wrong with the system (including being over-full), it is impossible for hydraulic brakes to ever lock up by themselves, no matter how hot they get.

 

 

Good luck getting the system cleaned up - it is not easy when it has been let go to the point you describe.

Goose

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The piston in the MC needs to move back far enough to leave that bleed off hole open. If it's hanging up occasionally this could be the problem.

 

When mine did it it was because I took too much free play out of the linkage. Piston didn't back off enough to uncover the hole. I doubt this is your problem as I think that would cause them to lock up every time.

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What is the level one should fill the front master to assuming the top of the cylinder is 'level'?

 

Service manual for MKII & RSV does not give a level for the front. It does say rear should be 2~5mm below bottom of hole. (MKII). For fronts it says to add fluid if below minimum level. (or similar)

 

:think:

 

Gary

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What is the level one should fill the front master to assuming the top of the cylinder is 'level'?

 

Service manual for MKII & RSV does not give a level for the front. It does say rear should be 2~5mm below bottom of hole. (MKII). For fronts it says to add fluid if below minimum level. (or similar)

 

:think:

 

Gary

 

Been too long since I opened mine, but I think most front reservoirs have a line on the inside about 1/4" from the top. That's where I usually set them. Bottom line is it needs to be low enough that the rubber bellows doesn't push any out.

 

BTW, clutch should be at minimum level. As the clutch wears the level rises. Opposite of brakes. Don't want it pushing fluid out.

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No I have Floor boards so I have to lift my foot to put it on the brake. I think my issue is multilayered.

1. Water in the line (evident from the steam coming out when the valve is opened)

2. The relief/return hole was clogged (cleared that)

3. Overfilling the reserve

I think that I'm going to delink the left front and the rear brakes. I will need to do some research what front MC to get and what length of braded lines I need.

Thanks for everyone’s help and comments. Any info on delinking and line lengths would be helpful.

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What info do you need to delink the brakes ?

 

The length of the left hose will be almost exactly the same as the length of the right one. If it's not stainless already, change both and use a 5/8" master cylinder (standard is 1/2").

 

I'm thinking back several years - after I delinked the brakes I removed the proportioning valve and then reconnected an additional line for the sidecar brake. You may find that you need a shorter banjo bolt (for a single, not a double connection) for the back and also a longer one for the front (for two brake lines not one) and can then just switch them round, but if your new front master cylinder has a different thread (ie off a kawasaki or something) then you'll just need to buy new ones.

 

Hope that helps.

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