Topic: Air in the System?

[Accolay]

1977 CB550F.

Can someone interpret this for me? Still trying to bleed these brakes. I open the speed bleeder and I can see that caliper A retracts, and leaves enough gap for the front wheel to spin freely. I close the speed bleeder nipple, and I get a hard brake lever. But now when I squeeze the brake handle, the piston moves out and doesn't retract.

Is there still some air in there locking down the piston when the nipple is closed? What do I have to do to make this work? At wits end.
Thank you.

[my78k]

I am sure someone will jump in and correct me if I am wrong but as I understand the workings of the MC there are 2 holes in it. The first and largest is the hole that the fluid is pushed through to activate the caliper and the second much smaller hole allows the fluid to flow back to release the caliper. Have you cleaned the second smaller hole out? Perhaps  if it is plugged it will prevent the release.

Dennis

[Accolay]

Thanks Dennis.
Both holes are good to go. If I pump too hard with the cover off, brake fluid pees all over my tank out of the small hole. The MC has been rebuilt. New SS brake lines/hardware. New speed bleeder nipple. New pads. New piston o ring. Original piston is good. Disassembled and relubed the caliper holder pin.

Now I'm looking into filling the system from the caliper end, or beating on it with a hammer and setting it on fire. One of the two. Walk away...just walk away...

[Accolay]

I bought another tool out of this. I decided to go with the Actron brake bleeder kit. I pumped out all of the air. Nothing but clean fluid coming out.

My question is, should new brake pads slightly drag on the rotor at all? I can spin the wheel, and it goes around a few revolutions and stops. I have a good and hard brake lever. I have adjusted the caliper holder screw so I get the most free spin as possible on the front wheel. I can see the caliper holder move slightly when I squeeze the brake lever, and it moves back slightly I can also hear the pads dragging a bit when the wheel is spinning.

Is this normal? Is there any brake-in time (no pun intended)?

[kghost]

Did you check that the stationary pad is not dragging or wobbling?

I often have had to put a Washer behind the Cotter pin holding them on the 750. They get just enough play to drag.

The piston doesn't retract very far.

I'd also make sure your rotor is not warped.

That makes them drag every time.

[lordmoonpie]

If your brakes are well bled and pumped out then it's possible to have the pads just brushing the disc at all times yes. It causes me issues racing in the wet sometimes becasue i use cast iron discs and sintered metal pads - sometimes the pad rusts stright onto the disc locking the wheel completely. If you have a hard lever you're doing well - don't worry too much about the pad coming back, any lateral movement in the disc motion will knock it back - you can't replicate that effect just spinning it by hand.

How much travel have you got in your brake lever? Just asking becasue I'm struggling to bleed mine up too. It's bled out as far as I can see no more air but the lever comes back to an inch away from the bar and is then rock solid - just wonderign if I should settle for that or keep on bleeding...

[GammaFlat]

As I understand it, the seal that the piston travels through can become hard over time and the piston slides on the rubber seal instead of distorting the seal a little.  This distortion (which is a good thing) then "springs back" when you release the lever and helps move your piston back "from whence it came".  I've tried it both ways a) use the old seals after a good cleanup and b) use new seals after cleanup and I think the new seals work better (but I hate spending the 30 bucks on the rebuild kit every time).  My input here might not be germane, however, because an old seal may give you a firm lever (but a dragging brake pad). 

[edit] egads, I've been robbed!   I didn't know you could buy just the seal (see post below).  All the extra crap in the kit (that you're getting charged for) is pretty unnecessary.  Next time I'll be looking for "just the seal". 

[Tom in Newcastle......Ontario]

I'm not sure but I think I paid,something like $8 Canadian for a new seal from a Honda dealer,,,,

[Accolay]

Thanks for the input fellas. After spending a few weeks on this problem I used the brake bleeder and the lever was good. I even took the MC apart again, just to make sure everything was right.

I couldn't take it any longer, and I rode the bike to work yesterday. The rotor was a little hot, but it didn't burn my fingers. I think maybe the heat is from normal braking friction?

I think my rotor might be slightly warped. Since I only have a few weeks (maybe) left to ride around, I'm gong to leave this problem for the winter months, or maybe spring...I saw the guy on ebay that drills rotors, spins with lathe  afterwards too.
http://cgi.ebay.com/ebaymotors/Disc-Brake-Rotor-Cross-Drilling-Yamaha-Honda-Kawasaki_W0QQitemZ160288686732QQi
hZ006QQcategoryZ111105QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Let me tell you about this tool- the Actron brake bleeder. Brakes bled in about ten minutes, probably could be done in less time if you know what you're doing. Awesome. I bought it because it was made out of metal instead of the plastic that the mity vac hand pumps were.

[scondon]

 Also of note is that as brake pads wear, more and more of the piston gets pushed out of the caliper body and stays there. Even though it is covered by a rubber dust shield it still gets exposure to the elements(dirt,grime,etc..). When new brake pads are installed the piston gets shoved back down and this dirty part of the piston can bind a bit on the seal causing drag.

   Some Simple Green and a toothbrush are good for cleaning the exposed piston before pressing it back in to install new pads. Not saying this is causing any of your brake troubles but it has helped me greatly reduce the "hot discs for a week" effect of installing new pads.