Front Brake problem 09 RMZ450 HELP!

bennytree
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bennytree
Edited Date/Time 5/31/2012 10:04pm
I tipped over in a corner and my front brake went out, never saw any fluid leaking anywhere.
Lever goes all the way to the grip with no compression.
I bought a "master cylinder replacement kit" and swapped all that out and bled all the air out and don't see any fluid leaking anywhere but still the same result, no compression. Help!
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Cygnus
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Cygnus 5/31/2012 9:26am
5/31/2012 9:26am
Any leaking down by the caliper?
lumpy790
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lumpy790 5/31/2012 10:41am
5/31/2012 10:41am
still a bubble in the system.....just like before you rebuilt the master cylinder.

Pull the caliper off the wheel and compress the piston into the caliper. This will push fluid and the bubble up into the master cylinder. I would do this several times. If it still is not 100% squeeze the lever to the bar and hold it. Crack the banjo bolt that holds the line to the master cylinder....a little fluid will squirt out....then re-snug the banjo bolt. It is very common for air to get trapped in this area.
Factor E
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Factor E 5/31/2012 11:14am
5/31/2012 11:14am
You may have knocked one of the banjo fittings loose enough to allow some air to enter the system.
tighten them and rebleed the system and see if the compression comes back.

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bennytree
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bennytree 5/31/2012 11:21am
5/31/2012 11:21am
lumpy790 wrote:
still a bubble in the system.....just like before you rebuilt the master cylinder. Pull the caliper off the wheel and compress the piston into the caliper...
still a bubble in the system.....just like before you rebuilt the master cylinder.

Pull the caliper off the wheel and compress the piston into the caliper. This will push fluid and the bubble up into the master cylinder. I would do this several times. If it still is not 100% squeeze the lever to the bar and hold it. Crack the banjo bolt that holds the line to the master cylinder....a little fluid will squirt out....then re-snug the banjo bolt. It is very common for air to get trapped in this area.
Last night I took the caliper off just to look around down there for leaking or anything. I did squeeze the lever and saw one of the pistons slowly move out so that at least works a little but lever still feels like it has 0 compression. I will try that a few more times then if nothing do like you said and loosen the Banjo bolt (do I just barley break it loose or unscrew a little?) Thanks in advance for the info. Very helpful.

I may take it to a buddy that went to MMI to check it out if I can’t figure it out.
dboivin
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dboivin 5/31/2012 11:25am
5/31/2012 11:25am
lumpy790 wrote:
still a bubble in the system.....just like before you rebuilt the master cylinder. Pull the caliper off the wheel and compress the piston into the caliper...
still a bubble in the system.....just like before you rebuilt the master cylinder.

Pull the caliper off the wheel and compress the piston into the caliper. This will push fluid and the bubble up into the master cylinder. I would do this several times. If it still is not 100% squeeze the lever to the bar and hold it. Crack the banjo bolt that holds the line to the master cylinder....a little fluid will squirt out....then re-snug the banjo bolt. It is very common for air to get trapped in this area.
lumpy got it right.

you need to compress that piston completely in the caliper (spread the pads). if you don't the air pocket behind it will never let you build pressure. i had this exact same thing happen to me last year.
bennytree
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bennytree 5/31/2012 11:39am
5/31/2012 11:39am
lumpy790 wrote:
still a bubble in the system.....just like before you rebuilt the master cylinder. Pull the caliper off the wheel and compress the piston into the caliper...
still a bubble in the system.....just like before you rebuilt the master cylinder.

Pull the caliper off the wheel and compress the piston into the caliper. This will push fluid and the bubble up into the master cylinder. I would do this several times. If it still is not 100% squeeze the lever to the bar and hold it. Crack the banjo bolt that holds the line to the master cylinder....a little fluid will squirt out....then re-snug the banjo bolt. It is very common for air to get trapped in this area.
dboivin wrote:
lumpy got it right. you need to compress that piston completely in the caliper (spread the pads). if you don't the air pocket behind it will...
lumpy got it right.

you need to compress that piston completely in the caliper (spread the pads). if you don't the air pocket behind it will never let you build pressure. i had this exact same thing happen to me last year.
Ok I will try pushing the pistons all the way in and try it again. Should I unscrew and take off the master cylinder cover when I am doing all of this or does it matter?
dboivin
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dboivin 5/31/2012 11:46am
5/31/2012 11:46am Edited Date/Time 5/31/2012 11:48am
leave everything connected...with lid off your reservoir up top. take caliper off, compress piston....if you have someone watch u will see bubble come out reservoir up top. then proceed to bleed like you would normally. should get some pressure within a few bleed cycles.

let us know what your result is as now i'm curious. if you had other issues (leak) you would know. this has to be solution.
ADynes
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ADynes 5/31/2012 11:56am
5/31/2012 11:56am
Can you build pressure eventually by pumping the lever repeatedly? If so, you may have a bent disc.
bennytree
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bennytree 5/31/2012 12:14pm
5/31/2012 12:14pm
ADynes wrote:
Can you build pressure eventually by pumping the lever repeatedly? If so, you may have a bent disc.
No, I have bled and pumped brake until I got arm pump Smile with no change in lever compression.
DrSweden
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DrSweden 5/31/2012 1:28pm
5/31/2012 1:28pm
Another tip, when the calipers are pushed in, take the lid of the master, open the bleeding screw attach a syringe (1 oz syringe on Walmart, for stuffing Turkeys) filled with brake fluid using a gasoline hose to the bleeding screw and push the air out by adding oil the wrong way.

Still this happened after a hit, one might suspect some mechanical damage somewhere?
Zycki11
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Zycki11 5/31/2012 1:35pm
5/31/2012 1:35pm
Got another brake question. My 12 Honda 450 was ok in the front brake. Had pressure with slack to pull. Wasn't tough or anything. Tipped over and broke the lever, put on the spare and now their is so much pressure it is hard to squeeze. I lubed the ball arm and everything else. We bleed the line and still no change. The lever can't even be adjusted further in because of the pressure that feels like is built up in the line. Any ideas?
PC
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PC 5/31/2012 2:13pm
5/31/2012 2:13pm
With the braking system full of fluid and sealed lay the bike on one side. Then flip it over and lay it on the other side. With any luck, the side to side movement will have forced the air pocket upstream into the resi and allow you to properly bleed it. If that fails then pull the wheel and start pushing pistons.

Cant say its a cure all for every brake bleeding dilemma, but its saved my ass on more than one occasion from having to actually pull out wrenches and do any real work.
bennytree
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bennytree 5/31/2012 9:59pm
5/31/2012 9:59pm
dboivin wrote:
leave everything connected...with lid off your reservoir up top. take caliper off, compress piston....if you have someone watch u will see bubble come out reservoir up...
leave everything connected...with lid off your reservoir up top. take caliper off, compress piston....if you have someone watch u will see bubble come out reservoir up top. then proceed to bleed like you would normally. should get some pressure within a few bleed cycles.

let us know what your result is as now i'm curious. if you had other issues (leak) you would know. this has to be solution.
It worked! Took the caliper off, pushed in the pistons, re-bled the brake and pumped the pistons back out and bingo! Thanks everyone.

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