Motorcycle Repair: Honda front disk brake, caliper piston, piston seal

Question
1988 Honda Shadow VT1100. Front caliper intermitently binds, slowly, while driving. Most likely cause is from heat build up from slight drag of pads on rotor. Only solution, so far, has been to crack the bleed valve which relieves the binding and allows normal brake function until it binds again. Entire front brake system has been rebuilt, new seals (in caliper), new pistons, new brake line, and new master cylinder rebuild kit installed. Believe that system has been properly bled because brakes are not spongy when applied. Yet, intermitent binding still occurs. I'm stumped, and so are several of my more experienced mechanic friends. Is this a problem unique to Hondas?

Answer
J. the caliper mount bolts go through sleeves that need to be lightly greased to all a little movement when the caliper is activated and released. Be sure that the caliper isn't hanging on the sleeves.

Be sure that some debris hasn't gotten down into the small bleed port in the floor of the m/c reservior. It is tiny and easily blocked. Sounds like something could be floating in and out of the passageway. From what you describe, it sounds like a hydraulic pressure buildup, which usually leads back to the m/c bleed port.

Calipers are certainly known to bind, when corrosion builds up behind the piston seal rings. Hopefully, you cleaned the grooves out thoroughly when you rebuilt the caliper.

Perhaps, you can try to apply pressure to the lever overnight (wrap a bungie cord around the brake lever and hold it tight to the handlebar). If the brake sticks after this test, carefully remove the caliper (if possible) to see if one or both pistons are sticking. If one is stuck, then the caliper piston is hanging. If both are stuck, the m/c is not releasing pressure.

I haven't heard that this is an ongoing issue with Hondas. Only caliper sticking and gunky m/cs generally are the cause of this condition. The same can happen to most any brake system.

http://shadowclubusa.com/forum/    I couldn't get the server to load a page, but hopefully it is a temporary problem. They should have some good suggestions for you, if this is a genetic problem.

Bill Silver