86 VFR700F rear brakes sticking badly

Hi everyone!  Hope someone can give me some ideas here...  Working to get this VFR700F back on the road and have run Into an issue with the rear brakes sticking.  Badly.  Have already removed the caliper and cleaned things up (the pistons, pins, new pads, etc) but have not rebuilt the caliper.  When I press the rear brake pedal the rear brakes do not release after.  To the point it's VERY difficult to even push the bike back in the garage.  Any ideas?  And thanks in advance for any suggestions you guys might have!!

12 minutes ago, JDizzle

Hi everyone!  Hope someone can give me some ideas here...  Working to get this VFR700F back on the road and have run Into an issue with the rear brakes sticking.  Badly.  Have already removed the caliper and cleaned things up (the pistons, pins, new pads, etc) but have not rebuilt the caliper.  When I press the rear brake pedal the rear brakes do not release after.  To the point it's VERY difficult to even push the bike back in the garage.  Any ideas? 

Yes.  "Rebuild" the caliper.

Did you remove the pistons when you cleaned them up?  Or at least pump them out enough to clean up the gunk/corrosion ring that typically forms at the dust seal?

Did you push the pistons in initially prior to any clean up to make room when fitting the thicker new pads?

Yes, I removed the caliper, pins, old pads and pushed the pistons out as far as I could to clean the gunk off of them (they were pretty dirty), cleaned the pins, etc and reinstalled.  I've done it twice actually, leaving plenty of clearance to reinstall the caliper. But then when you hit the rear brakes they grab and stay grabbed, basically.  I read somewhere about a 'return' hole or port in the master cylinder that can get blocked with debris or whatever....  Is that a possibility also?  I was going to try and bleed the rear brakes, replacing the old fluid with new as i did it.

Yes, that is possible.

I think I would be actually removing the pistons and verifying the seals on the caliper before moving on to the master.  The seals can get damaged/folded/swelled and have corrosion behind them (likely) and hold the pistons.

If they were as dirty as you let on, they are likely pretty corroded in the seal grooves.

OK.  Thx for the suggestions!  I'm going to get em outta there and see what we find.  I'll repost a little later with some pics...

Another thing that can go wrong is the old rubber brake line has deteriorated on the inside and allows fluid to flow one way and not the other. Seen it on cars before and I highly doubt that motorcycles are immune. 

So, Captain 80's, it appears you were right.  So far at least, Lol...  We got the pistons out, cleaned them really well, re-assembled, then bled them....and they seem to be doing fine now.  We have a brake pedal and they're not sticking atm...  Here's a couple pics and thanks for the tips man!

Awesome.

Pretty sure you mentioned it, but make sure that sliding collar for the lower mount bolt is clean, lubed and moving freely.

clean and lube or risk this

[image: post-3647-0-97799300-1460171157.jpg.87e76ddacf01578c3d90d349341987c0.jpg]

Thanks guys!  I'm going to have to check that because it began to stick again Lol.  Also the dust seals were a little messed up so I'm going to order some new ones.  But I'm going to have to double check that lower mount bolt as well. I'll post some more pics, etc soon!  Thanks again!