Can't get brakes after rebuild

Hi Everyone,
I'm having a helluva time trying to get some brakes on my 82 xj650. I rebuilt both the master cylinder and the caliper. No brakes after much bleeding. Assumed MC was rebuilt wrong, consulted on here, took it apart again - looks right. Thought maybe something wrong with MC that doesn't meet the eye so bought an aftermarket one on ebay. No brakes. Bleed, bleed, bleed some more. No brakes. Piston in caliper seems to be the center of the problem. Took it apart again honed the cylinder with a nice little hone that I bought at AZ. Wet sanded the piston again with 400 grit and miracle oil.
But here is what the problem seems to be: When you put the piston in, the seal doesn't seem to slide over the piston and let it pump up and down. I think the seal is twisting and binding against the piston. There are a couple of scratches in the side of the piston that I can feel with my fingernail. I've sanded them with the 400 and you can't feel them on your skin- they're so small you can only feel them when you slide your smallest fingernail across them and even then just barely. But could this be the culprit? Should I buy another rebuild kit and a new piston? Getting pricey but brakes are so good to have. Right?
Scott in Los Angeles

 

did you trying using a one-man vacuum pump / bleeder kit yet ???

 

If not leaking I say press on. The channel that the seals sit it have to spotless. More help here:

http://www.xjbikes.com/Forums/viewtopic ... rakes.html

 

I had a similar problem with my rd250lc when I put a stainless steel line in ,couldn,t get it to bleed . I used a primitive one man vacuum bleed kit. I stuck the end in my mouth and sucked like sh*t until blue in the face, worked a treat, cheers, Murray

 

this is the only way I've been able to bleed these brakes without going crazy.

http://www.harborfreight.com/brake-blee ... 69328.html

Also, what Adrian said... those seal channels have to be SPOTLESS