took my motorcycle out finally. and no rear brakes.

[vash]

I didn't ride all winter. for whatever reason, I cant ever remember.

I brushed off the webs, unplugged the Bob Kontak battery tender and it roared to life. I got to work easy. fun..smiling.

ride home, what? no rear brakes. took it easy all the way to my garage. no trail-braking, but no real danger.

got some Dot-4 sunday and bled the rears. easy enough, since the nipple and brake pedal are right there. all good. kinda fun, since the right and left hand know EXACTLY what each other are doing. bubbles came out, and fluid I thought was clean/clear not so much. its obvious when you pour in fresh the old stuff is definitely darker amber. all good to go.


got me thinking. how did air get into a closed system? my dot-4 degraded? turned to water? I will pick up some more Dot-4 and do the fronts before any spirited ride. the fronts will be more difficult since I have to squeeze the lever backwards and reach way down to the nipple. maybe I can get my wife to help.

[Tishabet]

I've had something similar happen to me in a car that I parked for about a year, went for the brakes and pedal went to the floor but would "pump up" like there was a lot of air. Topped off master cylinder reservoir, bled the entire system end to end, and everything worked perfectly again.

Then, because I could not figure out what the hell had caused the issue in the first place and could see no evidence of a leak anywhere, I replaced the master cylinder completely for peace of mind. Still puzzling over it to this day... where did my fluid go?

[Skip Newsom]

First hand experience is that brake fluid does very odd things if left alone long enough...
A couple photos from rebuilding my brother's 83 Interceptor after it sat for 25 years.

Found some that turned into a jelly like consistency and then some that hardened and became chunky mmmm chunky!





Brake fluid flushing is underrated, under appreciated and under consideration for the rest of my stable.

[Tidybuoy]

I had a situation where my rear brake failed - pedal had zero resistance. I flushed the system and bled and it held pressure for about one minute. I ultimately replaced the master cylinder. Bike had 16,000 miles and was 4 years old - it had been sitting for about 4 months and previously had been flushed once.

[manbridge 74]

The Gamma above is 35 years old. One of the first if not THE first thing I did was flush it with DOT 4 fluid. And soon I’ll pull back the caliper dust boots after removing pads and toothbrush off any debris on exposed pistons after pushing them out some...

[HardDrive]

My Duc sat for a year. I sent it off to the local Euro shop to get freshened up. Should have her back this week.

[rusnak]

Originally Posted by vash

I didn't ride all winter. for whatever reason, I cant ever remember.

I brushed off the webs, unplugged the Bob Kontak battery tender and it roared to life. I got to work easy. fun..smiling.

ride home, what? no rear brakes. took it easy all the way to my garage. no trail-braking, but no real danger.

got some Dot-4 sunday and bled the rears. easy enough, since the nipple and brake pedal are right there. all good. kinda fun, since the right and left hand know EXACTLY what each other are doing. bubbles came out, and fluid I thought was clean/clear not so much. its obvious when you pour in fresh the old stuff is definitely darker amber. all good to go.


got me thinking. how did air get into a closed system? my dot-4 degraded? turned to water? I will pick up some more Dot-4 and do the fronts before any spirited ride. the fronts will be more difficult since I have to squeeze the lever backwards and reach way down to the nipple. maybe I can get my wife to help.

Tell her you need her nipple twisting hand..

[javadog]

Originally Posted by manbridge 74

The Gamma above is 35 years old. One of the first if not THE first thing I did was flush it with DOT 4 fluid. And soon I’ll pull back the caliper dust boots after removing pads and toothbrush off any debris on exposed pistons after pushing them out some...

On a bike that nice, I would suggest fully disassembling the calipers and master cylinders and rebuilding them. Every single bike I’ve worked on from that era has needed it. People just don’t change the brake fluid nearly often enough. The rubber seals never had a 35 year design life, either.

[pmax]

Keep in mind your reflexes slow down as you age !

[rusnak]

For a Porsche, depending on which dealer you go to, they flush the brake fluid every 20,000 miles or two years.

For illustration only, here are the factory recommended service intervals for a Porsche Cayman S:
Engine Oil Every 10,000 miles or 1 year
Spark Plugs (Turbo Models) Every 30,000 miles or 3 years
Spark Plugs (6 and 8 cal / GTS Models) Every 40,000 miles or 4 years
Pollen Filter and Air Filter Every 40,000 miles or 4 years
Coolant Every 40,000 miles or 4 years
Brake Fluid Every 20,000 miles or 2 years

Brake fluid absorbs water from the air, and it turns to jelly. On a car with small brake servos and orifices for stability management and anti-lock, that would be very bad. Also dirt gets into the system via brake seals. Water can also cause rust and corrosion, also very bad.

[manbridge 74]

Originally Posted by javadog

On a bike that nice, I would suggest fully disassembling the calipers and master cylinders and rebuilding them. Every single bike I’ve worked on from that era has needed it. People just don’t change the brake fluid nearly often enough. The rubber seals never had a 35 year design life, either.

I plan to do this after I’ve gotten the titanium caliper pistons that are available. Helps that the PO was one of the most OCD guys on bike maintenance I’ve ever met. I changed all other fluids except in the rear shock and they came out almost as new as what went back in.

[wdfifteen]

Originally Posted by vash

got me thinking. how did air get into a closed system?

I wish I had an answer to that question. How does moisture get clear down into the bowels - right down to the wheel cylinders - of a brake system, when the only access is through the filler cap?

[javadog]

Originally Posted by manbridge 74

I plan to do this after I’ve gotten the titanium caliper pistons that are available. Helps that the PO was one of the most OCD guys on bike maintenance I’ve ever met. I changed all other fluids except in the rear shock and they came out almost as new as what went back in.

Those look like Nissin calipers off of something else, where are you getting the ti pistons for those?

[javadog]

Originally Posted by wdfifteen

I wish I had an answer to that question. How does moisture get clear down into the bowels - right down to the wheel cylinders - of a brake system, when the only access is through the filler cap?

Brake fluid absorbs it from the air.

[Nostril Cheese]

Originally Posted by javadog

Brake fluid absorbs it from the air.

This. happened a few times on my old CB750.

Add the relative use of the rear brake vs. the front and its easy for air/fluid to get past an O-ring.

I'd take the cylinder apart, clean well and lube everything up with fresh brake fluid.

[manbridge 74]

Originally Posted by javadog

Those look like Nissin calipers off of something else, where are you getting the ti pistons for those?

Good eye. It was common back in the day to install GSXR Nissin calipers, people are still making ti pistons for them. I do have the original calipers and wheels but they are a bit underwhelmed in this application.

[manbridge 74]

Originally Posted by javadog

On a bike that nice, I would suggest fully disassembling the calipers and master cylinders and rebuilding them. Every single bike I’ve worked on from that era has needed it. People just don’t change the brake fluid nearly often enough. The rubber seals never had a 35 year design life, either.

You could not here been more correct here. Noticed some extra effort needed to turn the front wheel. Tore them down, freed them up and lubed with Porsche caliper grease.

[LWJ]

Hey Vash, do you do the two syringe method? I did this on a dirt bike recently and it worked well.

Push fluid in from the bottom and bubbles exit the top.

[flatbutt]

I use the "open, pump, close" method. Open the bleeder, pump the lever, close the bleeder, repeat.

[Chocaholic]

Interesting setup. When I got my 08 Guzzi, there were no rear brakes. Turns out, the rear brake lever actuates the rear caliper and the front left caliper via a proportioning valve under the seat. The front lever actuates only the front right caliper.

Struggled to bleed the rear so I replaced the MC only to discover the bleed nipple on the proportioning valve. Ultimately cleared the air after bleeding the valve and the. the front left caliper by actuating the rear brake lever. Italian Engineering at its finest.

Actually it works quite well. The rear brake is noticeably more effective at slowing the bike than the front. Malto Benni!