I had the same issue with the front brakes on my '00 kx250...I cleaned the entire system twice, and bought 2 different replacement kits...nothing made them as strong as I wanted, like my K5's are.
Then I came across a couple posts/threads on here with guys experiencing the same problem, and guys threw on Honda master cylinders with great results. So I took the gamble, and found a 2012 CRF450 master on ebay for $80 if I remember correctly, bought new OEM banjo bolts and washers to go with it...I had to do a very light/easy mod to get it positioned where I wanted it...but the outcome is incredible!...I can just rest my finger on the brake lever now, and it wants to lock up the front wheel.
I don't see why this mod wouldn't work with the rear brakes as well.
Just another option to ponder.
**just pulled this off my thread...this is what I spent and bought.
been almost 30 years since I bought red bike stuff...that was for my 83 CR125 back in '86.
just picked up this '12 CRF450 master for $40, and spent another $55 for a lever, rubber boot, banjo bolt and washers, for my 250.
