mcman56 Posted August 22, 2016 Report Share Posted August 22, 2016 I have a 2014 evo and the rear brake has always felt weak. I finally went to diagnose and found that the brake fluid was black plus there was some black grease like goop around the bladder that fits in the reservoir. I cleaned it up and flushed fluid but then noticed there was a distinct step of resistance in the travel of the plunger. I replaced the cylinder and when I pulled the old one apart found what is in the picture. You can feel those bumps with your finger and it sort of looks like weld splatter. It looks like some is also in the cylinder bore but it is too small to get a good picture. The bore also shows machine marks that are not that smooth. Is simple corrosion the likely cause? Could it have been something bad in the fluid from the factory? This bike has low hours and I live in a dry climate but the retaining ring was quite rusty. Quote Link to comment Share on other sites More sharing options...
lineaway Posted August 22, 2016 Report Share Posted August 22, 2016 Most of the newer hydraulics are crap. Ever since 2010, but nobody wants to talk about the white elephant in the room. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted August 23, 2016 Author Report Share Posted August 23, 2016 The seal did not fail. There was no leaking of fluid. Interesting comment about new hydraulics. I have a 1988 Hawk NT650 with 63,000 miles and the hydraulics have never been apart, only flushed. Quote Link to comment Share on other sites More sharing options...
zuendapp Posted August 23, 2016 Report Share Posted August 23, 2016 Brakem Tec master cylinders had many problems in trials applications. Cut seals, metal shavings in rear master cylinders. One dealer had a rear brake failure during setup. My understanding this was in 2014. I'm sure others have more details? Maybe they have fixed some manufacturing problems now?? The seal did not fail. There was no leaking of fluid. Interesting comment about new hydraulics. I have a 1988 Hawk NT650 with 63,000 miles and the hydraulics have never been apart, only flushed. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted August 23, 2016 Report Share Posted August 23, 2016 possible causes: original fluid contaminated with water or particles remaining from manufacturing processes not cleaned out prior to assembly or item left wet and unprotected from corrosion following machining Quote Link to comment Share on other sites More sharing options...
thesolidman1 Posted August 24, 2016 Report Share Posted August 24, 2016 A little tip that may or may not had anything to do with your issue, the dust boot on the bottom where the plunger comes out actually traps and holds water in, so after riding in wet conditions and washing the bike, I roll the dust boot down and let the water drain out, and leave it down for a while so the moisture can dry. Quote Link to comment Share on other sites More sharing options...
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