Faulty master cylinder piston symptoms.

[chuckycheese]

I've had an issue with my rear brake on the big bike and am not sure what to do next. It stops OK (I can skid if I want to) but I have to apply quite a lot of pressure in order to get much stopping power. Here's what I know:

Pads...excellent and oil/grease free.
Lines...great shape
Fluid....clear, clean and free of air
Pedal....solid feel, short throw (not spongy, at all)

The brake is the same as the one on my 750. I've worked on it in the past and it operates perfectly. I'm guessing the problem may be the M/C piston....because I can't think of anything else. Any ideas??

[chef1366]

What type of pads are you using?
Is the rotor in spec?

[tkent02]

How old are the pads in years?
If they are fairly new, were the pads bedded in correctly?
If not it may have only about half of it's braking power being utilized.

[Nessism]

Maybe one of the rear pistons is stuck and all the braking force is coming from one side?

[chuckycheese]

thanks

Thanks for the suggestions, guys. The pads were on the bike when I got it but I've taken them out twice and they look very good. Both times, I lightly sanded them to make sure there was no grease or grime on them. The rotor is in spec and looks good.

It did occur to me that the problem may be with a piston, as Ness suggested. Both seem to be wearing evenly so I don't know if that rules out anything or not.

[Colin Green]

Thanks for the suggestions, guys. The pads were on the bike when I got it but I've taken them out twice and they look very good. Both times, I lightly sanded them to make sure there was no grease or grime on them. The rotor is in spec and looks good.

It did occur to me that the problem may be with a piston, as Ness suggested. Both seem to be wearing evenly so I don't know if that rules out anything or not.

Have you tried extending the pistons to full travel to make sure that they are ?

[chuckycheese]

No

Have you tried extending the pistons to full travel to make sure that they are ?

No but I think I'll pull the pads again and take a better look at what's going on in there. I'm pretty sure the caliper could use a good cleaning and rebuild anyway so I'll probably do that first.