Front Brake Issue

[bluegixxer600]

I have a weird one here. Just picked up an 86 VFR750, it's been sitting for quite a while, but was garaged and started occasionally. The front brakes will lock up while it sits. I have to bleed some fluid out to be able to move the bike. The next morning, the brakes are locked on again, even if I never applied them after letting a little fluid out of a caliper. I have bled the front brakes to get all of the old fluid out and left enough of a gap in the reservoir for any expansion. My first thought was there was moisture in the old fluid and it was expanding due to the warmer weather recently, but after flushing/bleeding there is no change. Maybe the rubber lines are internally swelling and compressing the fluid? I'll be changing them due to their age anyway. Anybody ever run across this before?
Thanks!

 

[Maddevill]

There is a little bleed hole in the MC. Could be plugged. If it was mine, I would rebuild the MC and the calipers. And put a modern front and rear end on it. And a FOX shock and...wait a minute. I did all those things. great bike.

 

[motomania2007]

Flush the brakes completely as possible but I sudpect you have brake fluid that has jelled and you probably need to disassemble everything and rebuild the calipers and mastercylinder

 

[DanvilleDSRider]

I believe that you will need to pull the calipers and clean the pistons.

I had the same problem I bleed them and they were fine until the next morning when the stiffness returned to the lever

This is a pretty simple process, I just did it last weekend for my sons CBR1000RR that has been sitting for the last 6 months.

Use some compressed air and it should force them out.

When installing the pistons back into the caliper please use a little brake fluid on them to make they slide in.

 

[bluegixxer600]

I'll check the bleed hole and probably get a MC kit. I have caliper seals coming already. This winter will be the modern wheel and front end upgrade:thumbup

 

[RickM]

I had a similar issue on an old brake system. It was due to a blocked port in mc. No amount of cleaning or blow with compressed air opened it. What sorted it was boiling(seals and piston removed) the mc in water and blowing with compressed air.

 

[Smash Allen]

I'll check the bleed hole and probably get a MC kit. I have caliper seals coming already. This winter will be the modern wheel and front end upgrade:thumbup

Very clean:thumbup

 

[mototireguy]

I had a similar issue on an old brake system. It was due to a blocked port in mc. No amount of cleaning or blow with compressed air opened it. What sorted it was boiling(seals and piston removed) the mc in water and blowing with compressed air.

+1 maybe this.

Stock or aftermarket front brake lever?

Some of the dodgy aftermarket flashy color levers fit incorrectly and never fully release on the brake master piston, pressure relief port doesn't open, causing this condition.

 

[bluegixxer600]

+1 maybe this.

Stock or aftermarket front brake lever?

Some of the dodgy aftermarket flashy color levers fit incorrectly and never fully release on the brake master piston, pressure relief port doesn't open, causing this condition.

It had a stock one with the tip snapped off, I replaced it with a stock one. There was no difference with the new lever. When bleeding, the MC action is smooth and it creates good flow. Sounds like the best course of action is to disassemble,clean, and reseal everything. I don't want to take chances with 30year old brakes!

 

[bluegixxer600]

Very clean:thumbup

Thanks!

 

[Maddevill]

An older,(93) GSXR1100 5.5 inch rear wheel fits right on. Same size axles. You will have to make spacers and an arm for the rear caliper that clears the wheel. Then you can run a 180 rear. Oh you also have to slightly modify the countershaft sprocket. Shave one side and put a spacer behind it. I had a custom stem made at Kosman and put an upside down front end on it from a GSXR1100 too. Then you need a shock with ride height adjustability to raise the rear up to a workable height. The bike looks SO much better with the fat meats on it and handles WAY better.

 

[bluegixxer600]

An older,(93) GSXR1100 5.5 inch rear wheel fits right on. Same size axles. You will have to make spacers and an arm for the rear caliper that clears the wheel. Then you can run a 180 rear. Oh you also have to slightly modify the countershaft sprocket. Shave one side and put a spacer behind it. I had a custom stem made at Kosman and put an upside down front end on it from a GSXR1100 too. Then you need a shock with ride height adjustability to raise the rear up to a workable height. The bike looks SO much better with the fat meats on it and handles WAY better.

Didn't think about using GSXR stuff, I'll have to look into that option. We have a machine shop here at work, so all the fab work will be low cost (beer or donuts) I bought it from a co-worker that is retiring soon and cleaning out his garage, he'd owned it for 22 years.

 

[Aware]

I had the same issue with a rear brake. I cleaned then eventually replaced the caliper, thinking it was seized or something - same issue came right back. Eventually I found a mechanic who explained how older master cylinders can choke up and the fluid cannot flow correctly, causing the brake to get stuck on. Replaced the master cylinder. Fixed.

 

[Hooli]

This would also be the prime opportunity to upgrade to some aftermarket SS lines, of course. :eboy

 

[bluegixxer600]

It was the bleed hole being plugged up solid. I took the master apart and found gelled, waxy old fluid. Gonna give everything a clean and reseal. Thanks for the help everyone!

 

[ST Guy]

I wouldn't dare ride that bike untill the ENTIRE brake system was COMPLETELY disassembled, cleand, inspected, and rebuilt with all new seals.

 

[bluegixxer600]

I wouldn't dare ride that bike untill the ENTIRE brake system was COMPLETELY disassembled, cleand, inspected, and rebuilt with all new seals.

That's the plan. It's in need of a thorough fluid change/flush for all compartments. I am doing the carbs right now, pretty gooey in there too. Seeing the hardened brake fluid will make you want to bleed your brakes yearly. Brake fluid is too cheap to let it gum up like that. I knew what I was getting into when I got the bike, so I'm in no rush to ride it. I'll just be happy to be able to move it around the garage without the front brake sticking on:thumbup