Topic: Brake Lever Play - 75 550F

[Dr. Noisewater]

Hey guys I rebuilt the front brake caliper on my CB550f and everything seems to work, but the lever has more play than it should.

It has about an inch of play before it actuates anything. It will lock the tire if I grip hard, but it's almost touching the throttle at that point.

I read about sticking a piece of fuel line into the hole under the plate on the bottom side of the master cylinder, but how much tubing? I shoved about 1/4" of clear tube in there but nothing changed.

It has new rubber lines and I'm certain there isn't any air in the system.

Also, the manual says to adjust the stationary pad to .006" clearance. With a feeler gauge between the pad and rotor? I adjusted the stationary clearance based on whether it was rubbing against the disc or not. It's as close as I could get it without it squeaking against the rotor as I roll it around. Hope that makes sense..

Any clarification would be great. This is my first brake job, and first vintage bike so my experience in these matters is non existent. Thanks!


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[flybox1]

lock the tire?  while riding, or just when spinning it by hand?
even with a poorly bled system, you may get some pad movement.  Probably enough to stop a hand-spun wheel.
Sounds to me like additional bleeding is necessary.

yes, you should be able to get that .006" feeler gauge between the stationary pad and rotor.

[Dr. Noisewater]

While riding it'll stop the tire.

I'll try to bleed it some more, and check with a feeler.

Does anyone know what length of tube people typically stick in that hole under the master?


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[LesterPiglet]

If your lever is almost touching the bar when actuating then you still have air in the system. Pump the lever a few times and hold it in with a cable tie overnight.

[Dr. Noisewater]

Hmm sounds interesting. Can you expand on it more? Should I bleed it more before that or just pump it til it's stiff then use the cable tie to hold it? What is this supposed to accomplish and how? Do I continue to bleed it when I release it in the morning.

Thanks for the suggestion.


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[flybox1]

pumping it wont release the bubbles.
with new lines, those tiny bubbles easily stick to the lines and in bends, and can be difficult to get out unless you have a pressure bleeder. or bleed the system from the bottom, up.
since you're half way there, rubber banding/zip tie, etc., the brake lever to the handle holds the return hole open, and allows any bubbles to slowly evacuate. turning your bars to the left also makes a more vertical path for the bubbles to flow to the MC.
its just going to take some time and patience on your part.  set it like this overnight.
maybe warm the lines with a hair dryer to make the air bubbles expand and rise.
tap on any bends/connections/banjos to help them release.

[LesterPiglet]

If you are sure you have done all you can to bleed it just pump it till you get the best pressure, tie it in and leave overnight. Next day release the lever slowly and it should have stiffened up. The micro air bubbles are forced to rise up the pipework to be realeased in the MC..I'm led to believe. I presume holding the lever in will help the bubbles bypass the brake switch as well.

[Dr. Noisewater]

Great thanks for explaining guys. I'll try those methods and report back.

Thanks again!


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[alacrity]

Check the disk thickness with a micrometer in a few places also--be sure you are within spec.  Also triple check the manual and parts fiche to be 100percent sure you have the caliper on and spring correctly etc.  If there is no air n your line and if you have a good rotor and if you have a not bent lever and stock lever mount and if you have a fresh piston seal allowing proper extension/retraction of the caliper piston, then the aforementioned lever will never come to the throttle no matter how hard you squeeze it.  I can do a full on stoppie with three fingers pulling hard and there is still plenty of room for my pinky


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[Dr. Noisewater]

Well my certainty of having no air in the system was false. I bled it more yesterday and had a few bubbles come out. I then pulled in the lever, secured it with a cable tie, put it on side stand, cocked the bars left, and left it overnight. I released it this morning and it feels amazing. Haven't ridden it yet but the lever is much stiffer than before and doesn't come nearly as close to the lever.

I still have play in the lever before it actuates the master though, I wasn't expecting the bleeding to cure this but I'd still like to fix it. The lever can move about an inch before any pressure is felt. Anybody have any experience with this on 550's? From what I've read they don't have a free play adjustment on the lever or master anywhere.

Thanks guys!


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[LesterPiglet]

Mine has this bolt under the MC which I believe is for travel adjustment, I haven't ever moved it though. This may be the same place a previous poster suggested putting a piece of plastic hose.

[Rgconner]

That lever does wear over time.

[Dr. Noisewater]

A little update.. I finally took the bike out for a proper shakedown today and put it through its paces. After re-bleeding and leaving the lever in overnight I'm confident I got all the bubbles out. The lever feels really good.

But.. now that the air is out and I can really feel what's going on in the system, sometimes when I'm coming to a stop the lever will gradually lose pressure and eventually be pulled in all the way. The wheel is stopped, but barely. If this were to happen in an emergency I'd be F'd.

My guess is the master cylinder needs rebuilding. There is also some really dark liquid coming out of where the lever goes into the master cylinder. Not much, but speed will cause it to smear down the lever. I have a rebuild kit that I never used so maybe now I can.

And btw, I solved the lever play issue. I took off the plate covering that little hole under the master cylinder, scooped out the gunk that was the original "bump stop" and shoved about 1/2" of rubber tubing in there. Then replaced the plate. It really looks like this was an "after the fact" solution for Honda, which would make sense why the later models didn't have such a primitive solution. I love old engineering.

[LesterPiglet]

Good to hear you have a rebuild kit, sounds like you need it. I needed one for mine but bought the MC pictured above for less than a kit.   

[dagersh]

The problem you describe is also an indication of air still in the system. Since you are rebuilding the MC, also upgrade to new SS lines. Then re-bleed the entire system. Brake lever fade WILL get you killed.

Nothing more important than good brakes on a bike. Whatever the cost-

Amen. 

I am thinking your system is exposed to sir through worn MC internals.  Definitely rebuild it.  Make sure after cleaning up that thye bore of the MC is not comprimised.

Do search on Youtube for rebuilding a honda MC, great info and how to's.

The SS Line is always a great idea. 

Keep us posted.

Gersh

[Dr. Noisewater]

Great thanks guys. I will rebuild the master cylinder next weekend. I'm going to stick with rubber lines for the time being, they're brand new from slingshot cycles. I bought them about a year ago when starting the build cause I didn't know any better, but I'll get some SS lines in the near future.

I'll update with the results.

[Dr. Noisewater]

Well I just got done rebuilding the master and putting it back together. It seems perfect now. No play, no leaks, and a nice firm grip that can't be pulled to the handle. It actually wasn't too bad of a job. There's a few videos on youtube that clear up any questions, and I was able to get the retaining clip out in just a couple minutes with a pair of dental picks.