Any suggestions on getting this thing cleaned out?

Yeah.  It's pretty bad.

I'll try the brake cleaner sometime this week.  I live in a very wet climate (and I can't garage the bike), so should I let it dry with the MC cover on loosely, or tightened all the way down?  I'm thinking a day or two to dry.

Versy, if you spray it all out with brake parts cleaner and get some inside (that remains wet) what will that do to the new brake fluid?  

Brake fluid is alcohol and glycerine based and brake parts cleaner is acetone based .....

I can understand not letting it stay out unprotected ("dry") for days & days (rust and worse would come to see you fer sure) but the only protectant you can put on it is new clean brake fluid and that gets contaminated very quickly with atmospheric moisture if you leave it out in the moist air for any time at all.

I'm curious, as I don't know the total answer here .....  likely he has the same greasy crap down inside his piston & cylinder and in all his hoses.

Do you think some fresh clean brake fluid could act as a slow acting clean up solvent (pump it out / bleed it out a couple of times over a period of weeks to get the sludge out) or does he have to take his whole system into little bitty wee pieces and clean out each & every piece?

  I know which path I'd try first .....

Just go to Walmart and get a couple cans of denatured alcohol. Drain the entire system best as you can by gravity, close the bleeder, fill the system with the d-a. Let it sit for a couple days and drain it. Repeat until the d-a comes out clean, then fill and bleed as normal (for most bikes, reverse bleed works better, fill system through bleeder with a pump) with DOT 4 fluid. In the PNW, you might want to do at least a partial bleed/refill a couple times a year. The master cylinder cap gasket WILL allow moisture in, regardless of how tight the cap screws get seated.

Trust me on that, born and raised in the Puget Sound Basin, have spent many a day in Oregon on Sauvie Island (yeah, Collin's Beach) or at Seaside, or visiting relatives in Oregon City/Milwaukie/Gladstone/etc.

Single_Spark wrote on 06/24/13 at 21:41:56:

Yes, alcohol is the only means. and it should be used insideyou.  
but seriously, the first cleanse brush master cylinder from the dry scale, and then wash thoroughly with alcohol.. you can still try the carburettor cleaner.

Denatured alcohol sounds good, but try to find out what was used as a denaturant. Sometimes alcohol is denatured with another alcohol such as methanol (wood alcohol); sometimes with gasoline.

Dave wrote on 06/25/13 at 05:09:51:



I agree.  If the reservoir looks that bad, I'd have to question how far the rubber has deteriorated, and how pitted the piston bore in the caliper is.  Disassemble, inspect, clean and replace as necessary.  And Dave may just be onto something with the silicone fluid.....just be forewarned that it is not at all compatible with regular fluid, and can be hard to find.

Unfortunately, not everyone has a HD or any other power sport dealer in their neck of the woods.  NAPA is the only parts store that even seems to know what it is around here, and they have to order it (usually next day).