front brakes locking up

[DEATH4OF4]

i got some new levers for the fz. when i was replacing the brake lever the plunger for the hydraulic system fully extended (not knowing) i tested the brakes buy squeezing the lever they seemed fine without the bike running. i drove it for a bit no probs but when i got on the highway at about 65 the front brakes started to lock up which gave me a good stoppie. i didn't dump it amazingly. i got of the road put the bike in neutral and she wouldn't move... locked right tight. not good. the lever would not move either. i waited for a while until the brakes let up and was able to drive home not using the front brakes at all. tried it again today around my tiny block and they locked up again....now like i said "not knowing" i shouldn't have let the plunger all the way out... so now do i just have to bleed or replace the fluid and I'm good to go?

 

[macem29]

bleeding removes air from the hydraulic system, if the brakes are locking up
it's another problem, like the lever is wrong, or out of adjustment...
if the brake pads are dragging when things heat up they will bind on....
I'd try putting the old brake lever back on and see if the problem goes away,
any instructions with the new levers?

 

[Erci]

The reason they are locking up after a bit of riding is because they are dragging. As they drag for a bit, the fluid begins to heat up which causes expansion. Eventually it expands enough to push hard enough on the pistons to lock the wheel.
Try to lift the front off the ground and spin it.. listen for drag.. it will almost certainly be there. You can also try to put stock lever back on and spin it again. I am betting it will still drag. At this point, you will want to bleed it and once again test for drag.

 

[lomax]

I would highly suspect that your front brake lever is out of adjustment. If it does not release ALL of the way the pressure will not bleed back into the resivour. Make sure the brake lever has some free play when it is at rest.

Marc

 

[Razer]

This happened on my snowmobile(also Brembo brakes). Changed brake handle piston came out releasing dirt into the system. Bled system, changed fluid, bled out air, and good to go.:thumbup:

 

[DEATH4OF4]

There was no instructions with the levers. I will try to see if I can find some way to adjust them. I think if I had some one to hold the plunger in I would have these problems. Also I will try to change the fluid and bleed it. If that don't work then I'll have to use the old levers. If anyone has any more ideas let me know... Thanks for the responses

 

[FinalImpact]

I would highly suspect that your front brake lever is out of adjustment. If it does not release ALL of the way the pressure will not bleed back into the resivour. Make sure the brake lever has some free play when it is at rest.

Marc

^+1

Ditto + it needs bleed!

Or another reason they lock is that the brakes master cylinder piston is partially depressed. << Its out of adjustment!

In a nutshell as you pull on the lever it moves the piston. But before the piston moves, the master cylinder uses the reservoir to load the chamber with brake fluid through a small feeder port. For the brakes to build and apply pressure, the piston movement down the bore seals the feed port from the reservoir so pressure can build in the brake line to the caliper.
IF - IF the piston is partially depressed it closes that port! BUT - the brakes still appear to work fine as they apply pressure and release pressure. But - with the port blocked, the expanding fluid can not return to the master cylinder as heat builds. The next place it can go is to force the caliper pistons outward and apply the brakes as it did in your case.

You see now how this whole thing gets worse with just a little heat. mainly from the brakes being applied but even sunlight and engine heat will expand the fluid.
-> Loosen the adjuster so the lever has free play.
-> Adjust to specification
--> Bleed the brakes and you will likely be OK.

Also check the pads and make sure nothing was worn or damaged and needs replacement after being heated like that.

 

[DEATH4OF4]

Is there a section in here to show how to adjust the front brake lever? Im not sure where the adjuster is.It's funny what little adjustment makes Big difference. I took it out last week with no problems at all...put different levers on and bam problems. I will be trying something when I wake up it's suppose to be 54 degrees whoo hoo

 

[TownsendsFJR1300]

I would highly suspect that your front brake lever is out of adjustment. If it does not release ALL of the way the pressure will not bleed back into the resivour. Make sure the brake lever has some free play when it is at rest.

Marc

+1 on the above, especially since it happened right after the new lever was installed.

BTW, are the levers cheap knock off copies? I ask as sometimes parts from China are not machined as well as others.

In the master cylinder, on the handlebar, there's a stop retainer that keeps the main piston/piston rod from coming out, thus, it won't come out beyond its limits unless you remove the retainer.

Sounds like the lever is not letting the piston rod come out all the way as it should. Its slowly building up pressure each time you pull the lever until it locks up...

 

[DEATH4OF4]

Yup... Ya got er. Upon closer inspection of the original lever and china lever shows the the china lever has a more shallow hole. I should have looked closer. It will need to be drilled out about 2 8ths to work. As soon as I put the old lever on I noticed it right away. Brakes are fine now.I should have got pazzos. Thank you guys for all the help.big thanks. Well if nothing else I got a front brake fluid flush it needed it anyway.

 

[FinalImpact]

Did the master cylinder (MC) piston fall out on the ground? If so, I'd want to make certain the outer lip didn't get torn or gouged during re-insertion into the MC as it could lead to unexpected brake failure! :thumbdown:

Remember NO OTHER fluids other than brake fluid should be used to clean this part. Also as Townsends points out, where is the retainer clip and why did it fall out? That clip helps maintain proper porting and valve alignment. Please double check everything before riding it!

 

[Evitzee]

Yup... Ya got er. Upon closer inspection of the original lever and china lever shows the the china lever has a more shallow hole. I should have looked closer. It will need to be drilled out about 2 8ths to work. As soon as I put the old lever on I noticed it right away. Brakes are fine now.I should have got pazzos. Thank you guys for all the help.big thanks. Well if nothing else I got a front brake fluid flush it needed it anyway.

Good you figured out what the problem was which could have been a serious safety issue out on the road. It's also a good lesson in using cheap(er), usually Chinese made, parts instead of higher quality stuff. In this case a Pazzo or ASV lever would have fit perfectly with no issues. When I put on my ASV's you knew you were dealing with a quality product, if for no other reason a US or Canadian company couldn't afford the insurance liability costs of using and selling ill fitting products in something so critical as a motorcycle braking system. A couple of lawsuits with a product that was defective and they would be out of business. If it was me I'd throw out the Chinese cheapies and get some GOOD levers, do not try to drill out or adjust the junk levers you now have, the tolerances are too critical.

 

[DEATH4OF4]

i did end up putting those china levers back on i drilled it out so the piston fits perfect. i drove it all day with no problems. i think they should have said the levers may need to drilled out to work properly.they didn't even have instructions, some one could die.:spank:

 

[TownsendsFJR1300]

You get what you pay for....