Rear MC Seal Crossover Help

[bkoz]

I am chasing poor rear brake performance on a friends '13 EC300. I am thinking that it needs a master cylinder rebuild.

The master cylinder looks very similar to some Japanese bikes. Does anyone know what rebuild kit would crossover?

[Moto7man]

Look on the mc for the name of the mfg. it's probably a Nissin. Also, check for a deformed bleed nipple on the caliper. Some people have had bad brake performance because the bleed nipple was deformed during installation at the factory.

[barossi73]

bad performance in what way?check the brake lever is set right and not just hitting the stops a fraction early.obviously if its miles out it will clunk but if its only just hittin it wont unless you stamp it.theres not a lot of room for the required travel if you lower the pedal on the 13.also check caliper is sliding/floating freely and disc is not slightly warped/bent.this throws the pads further apart and requires more pedal travel to actuate.cracks allowing pad material to lift slightly can also cause this and a spongy feel.if the seals are shot youl most likely get some weeping at the rubber boot under res.give it a good squeeze to check.also flip the caliper and look closely for weeping around the piston boot,press piston in a little to confirm its not ceased.will be stiff but not rock hard
also have a look behind the chassis rail where the lever goes behind it for trail trash.i had some shrubbery get caught in there,was almost invisible but was just enough to prevent/dampen the last bit of travel that locks up the rear

[bkoz]

Originally Posted by barossi73

bad performance in what way?check the brake lever is set right and not just hitting the stops a fraction early.obviously if its miles out it will clunk but if its only just hittin it wont unless you stamp it.theres not a lot of room for the required travel if you lower the pedal on the 13.also check caliper is sliding/floating freely and disc is not slightly warped/bent.this throws the pads further apart and requires more pedal travel to actuate.cracks allowing pad material to lift slightly can also cause this and a spongy feel.if the seals are shot youl most likely get some weeping at the rubber boot under res.give it a good squeeze to check.also flip the caliper and look closely for weeping around the piston boot,press piston in a little to confirm its not ceased.will be stiff but not rock hard
also have a look behind the chassis rail where the lever goes behind it for trail trash.i had some shrubbery get caught in there,was almost invisible but was just enough to prevent/dampen the last bit of travel that locks up the rear

Pedal is brand new. The brake has a mushy feel even after bleeding via a Mityvac. Prior experience says that it feels like a a bad MC piston seal. No external leaks.

[2taddict]

If Nissin check kit part no's against crf450x. My 05 looks exactly the same as 07 Honda