Severely Binding Front Brakes. (Gen3, 1990)

Our 1990 VFR 750 with 30,000 kms sat for about 2 months. I went to move it and the front brake calipers have almost seized tight on the discs. Bike was very hard to move/roll in my shop. I can’t turn the front wheel by hand with the wheel off the ground. This bike has been very impeccably maintained, kept spotless clean and has fresh brake fluid. Where should I start?

 

Been there, done that, don't have a t-shirt either, good morning anyway. Start by, removing brake cover for your master cylinder and suck fluid out/you could use a paper towel to get some out too. Loosen allen cover and the long bolts associated with holing brake pads in. Remove both calipers from the stanchion and and use a brake piston holding tool or a block of wood/maybe two and slowly operate the front brake lever.

The idea here is to push the pistons out of the bore of the caliper, you will get the hang of it believe me. I have some nice internal cir clip pliers that I grab the inside of the pistons with (never grab the out side of the piston with pliers!) and I remove all the pistons, once you remove them, remove banjo bolts and walk away with both calipers and piston, keep them together as I dont like to co-mingle stuff, and here is where the real work begins, your gona use a wooden 0r plastic tool to remove the seals and start cleaning with wood tool or plastic tool, (you could wrap a metal pick with some scotch-brite, I like wrapping some 1000 sandpaper around something and getting into the grooves (it is groovy )and go to town on the bores where the piston seals are, problem is there is mug/ orrosion and smiggma there preventing piston from retracting. Once your done there, you can clean the pistons (assuming they are not corroded) and your set to re-install, I have used seals again and have had no ill affects you just have to examine them real closely. You could get K&L or OEM. I would do OEM. Anyway, lubricate the pistons with a little brake fluid and install them.

Your gona have to bleed your brakes, I replaced all my bleeder valves with oem stuff and had problems. I ended up getting some nice stainless bleeder valves and was happier than a pig in chit. No weepage etc. I have a mityvac bleeder that goes to my air compressor. I would consider re-building your master cylinder and clutch & replace your clutch slave - but that is just me. You could pull the lever off and remove the rubber and take a look inside with a flash lite and see if there is calcatrated chit in there. I am sure I forgot some stuff, not rocket science, its the stuff you have to put up with if you wana ride a 30 year old bike. Be glad you don't have any linked brakes or heaven forbid abs crap. CHeers

 

Thanks for the info. I was hoping that I would not have to go through a full caliper rebuild......... I have rebuilt calipers before, at least I have all winter. Do you have any insights as to why it would do this when its in a nice warm garage and it has very rarely seen rain? Just old seals???? Pics to come as I tackle the job.

 

The brake fluid is hydroscopic so it absorbs water, the bores on the calipers are just regular aluminum so it kind of just goes hand in hand, the manual wants you to change brake fluid 4-5 years I believe? No-body really does that until it looks like mud through your sight glass or you have problems like your having. My 91 is high mileage perfect running bike you could hop on and go anywhere. I was wheeling it off my lift and felt some resistance going backwards, I knew right away my caliper had issues, long story short I took the rear caliper apart cleaned it and that was it, I think I even reused the main seal and dust seals and job was complete (I had 60,000 miles on rear pads too give or take, can you tell I don't use rear brake that much.) I never rebuilt the rear brake master cylinder on any of my bikes or customers in the past btw.

I did the front calipers on this 91 maybe 20 years ago, I recently within the last year or two did them again, originally when I did them I had access to some aviation anodizing material which I utilized, when I did the repair/cleaning the bores looked good with out too much mug behind the seals. Anyway, its not so bad, just think, it could be the last bike you ever have to buy, I have two of them.

 

always eager to avoid any serious work, i'd suggest that you remove calipers and their pads, then clean the piston area with a toothbrush and dribble some brake fluid into the horizontally placed calipers around the pistons. then try to work the pistons back and forth using brake lever and carefully-applied pliers.

the old "in and out" just might be all she needs, and it's worked for me.

 

The weird thing is that the brake fluid on this bike has been changed annually. I did not expect it to lock up like it did with no other signs during the summer. I am used to maintaining our fleet, my wife has this 1990 750 and a 2002 800 ( non abs fortunately). I have two Ducati ST3’s. I spend more time wrenching on the VFR’s than the Ducs. Doh.....

 

Try cracking the bleeder to see if the pressure comes off? If it does....

 

Take the pad retaining pin out, open the bleeder , insert a screwdriver or likes between pad ends and apply a bit of pressure to force pistons back a touch. Close bleeder, remove pads.

Your next job will be to check which pistons are sticking. You may be lucky enough to get away with bit of brake grease on pistons after a clean, at worst replace caliper seals.

 

That aint "Sagitarius' work though

 

It is possible that old seals are hardened from brake cleaners/environment, time for new ones perhaps. Pistons should always be cleaned before any pad replacement in case there's dirt/ridge pushed back into the seals. All that said, you may have checked all that..... Every time I put new seals in a caliper of any age, they always work better. Of course, caliper slides have to be free as well.

 

One of my bikes that I restored the brakes 2 years ago (new pads, pins, seals, polish pistons etc, etc, had a stuck caliper. I had only done 10 miles on it but 2 years ago when I got it mot'd - lol..
What I now do is push the pads back on the bikes I'm not planning to use for a while now.

 

You might get away without rebuilding the calipers if the problem is a seized slider pin. This is common and causes the same problem as well as a collapsed brake line. It sounds like it was fine when parked so probably not the brake line. I would start with cleaning and greasing the slider pins and if that isn't the cure then proceed with the calipers.