Topic: 750 SuperSport rear disc brake question.

[GroovieGhoulie]

My dad just got himself a nice 750F and I am the one doing services on it since I am the "Subject Matter Expert" in the family.

However, I don't know much about the rear disc on the 750F models.

How freely should the rear wheel turn when turned by hand on the centerstand?  I ask because I think the rear brake is not releasing all the way.  The wheel can be muscled into turning and when let go, stops within a quarter revolution.  My 400F's rear wheel freely spins with little effort.

How to adjust the rear brake to make sure it is releasing all the way?

[cben750f0]

mate it should turn freely, i thinks its time for an overhaul, ...peace

[Gabus]

Yup..should roll freely. Most likely caliper piston draging. Take a rubber hammer, give the outside ( the round part) couple wacks, if the wheel now turns freely your caliper is sticking. There is no way to adjust for the sticking. Mine had a lot of build up in the seal bore (common problem). I replaced the piston and seal and cleaned the bore. There's also a very small port in the rear M/C that could cause the problem.

[upperlake04]

Ghoulie - I asked a similar question a while back. http://www.sohc4.us/forums/index.php?topic=8128.0 Master DD replied some rub is normal and crazypj offered some good technical advice on adjustment.
   My bike is still not on the road so I can't report if there is a problem or not with the small amount of drag after  disassembly/clean/reassembly of the old parts. With the chain off, I get about one revolution of spin with a moderate shove.  Maybe some other F owners will  let us know about their rear brake arrangement.
  It does seem that no pad/disc contact would be ideal though.

[Gabus]

How's it feel when you sit on it and roll the bike? Mine was noticeable just rolling it out of the garage.

[GoatBaSS]

Yup it should be free man FREE!!! Check and see that the caliper and holder are lined up, no weird bends, dents. Make sure it is not something else that may be holding it back, spacer, sitting wrong in the swing arm, etc. Once running, take it out and be hard on the bugger. It may have set due to use.

[Honda CBer]

or rebuild the caliper... dirt gets trapped around the o-ring to the point that the piston drags... only way to fix that is to disassemble it...

[Clyde]

You will get some gentle rubbing/touching, but nothing that will stop the wheel that quickly.
There is no adjustment other than for pedal height
The rear disc on the F/F1 has a dual piston caliper and if either piston/seal is corroded or stuck you will get binding. They are not a great design and the F2 changed to a single piston caliper which is much better.
Mine has had to be rebuilt and my friend has just rebuilt his again, after initially rebuilding it about 5 years ago. When he picked the bike up back then, the back wheel was locked solid and we used a screwdriver to prise open the pads to be able to move it
I would advise pulling apart the caliper and replacing both piston seals and the o-ring that seals the two halves of the caliper, as well as cleaning out the caliper and the seal grooves(most important)
Regds Clyde

[GroovieGhoulie]

I will probably have to rebuild the caliper with new seals and such.  The bike has 700 miles on it and it sat for a LONG time in the PO's basement.  The PO said that he serviced the brakes, and while they work, the bike is HARD to push aaround while sitting on it and I think that the dragging brake is sucking some HP away.

The front brake spins fine, but needs a minor adjustment.

[kaceyf2]

Just as a "double check" undo the caliper, hold it up and out of the way, and then try spinning the back wheel, just to make sure that it is the brake sticking and not a more serious problem like wheel bearings etc....better to be safe than.......
then follow all the good advice on rebuilding the caliper.