Topic: brake lever will not retract - CB550K1 1975

[tkarahalios]

So about two years ago I rebuilt my master cylinder and my front caliper. It has been fine for 2 years. Today I tried bleeding and flushing the master cylinder on my 1975 CB550K1 and the brake lever is not retracting so the front brake is dragging. When I push the lever back manually the caliper releases.

Does this mean the problem is in the master cylinder and not in the caliper?

Is it possible that since the bike has not been ridden since last November this is a problem that will go away with a little slow careful riding around the block?

Since I have rebuilt the master cylinder two years ago with OEM parts, do I just need to do it again? Should I do anything different like try to hone the master cylinder bore if I can find a tool small enough?



Any advice appreciated. I'm eager to get out there. The weather is getting nicer!

[NobleHops]

Eliminate the simple possibilities first. Loosen the locknut on the underside of that pivot bolt and then the pivot itself and see if the lever is binding in the perch.

Then open up the reservoir and remove the diaphragm. Is the fluid gelatinous and cloudy? Pluck a wire strand from your least favorite wire brush, clamp it in some pliers and see if the return orifice (smaller of the two) is clear.

Inspect the caliper and the lines. Any obvious binding, wear, damage? Sometimes old brake lines will collapse on the inside and make a sort of check valve, not allowing fluid to return. What's the story with the brake lines?

If all this proves fruitless, go for the full disassemble, clean and fluid swap, and blast out the brake line while its apart. You can reuse the seals and parts if you're careful on disassembly.

Report back, tell us what you discover please.

N.

[strynboen]

the piston are stock in the full pulled posision..a easy and dirty vay is to blow air backverd in the pibe end. blow the piston back (carefull).but better is to take the marster off the bike..and make a total kelan up..there is stuck some dirt..and better get it all kleaned up
often you dont need new parts...just a klean up of all aluminium parts..

try to loosen the bolt vho the handel turn over..it have to move vitaut any friktion..

just as (n)have pointed aut!!!!!!
you need a speciel Tool to get the clip Lock aut..but you have beed there before,,

dont do anything to the bore..its soft polished aluminium(not cast iron) like old cars..(so no honing)

[tkarahalios]

Thanks guys. It turns out "NobleHops" was right. I had replaced the levers this winter and forgot I never rode the bike since then. Turns out I had overtightened the brake lever screw and there was too much friction on the lever. I loosened the screw and everything is back to normal. No need to rebuild the master cylinder...saved me a bunch of time and headaches!

This forum is great for checking in before investing time and energy to do something that might not need to be done.
Thank you!

[NobleHops]

Cool, glad you got off easy! Thanks for closing the loop.

N.