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Filling new brake lines

NPS

NPS

Cruisin' Guzzisti
GT Contributor
Joined
Dec 11, 2008
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Location
Churchdown, Gloucester, UK
I have replaced the front brake pipes and refurbished the slave and master cylinders with new seals on my Guzzi Breva I'm restoring.

I have had difficulty before and I would be grateful for any tips to fill the front brake system with fluid.
I remember a previous preponderance. I worked it out but took hours.

Do I start at the bottom and fill each caliper with small pipette drips. Then suck fluid into each hose and connect at the bottom. Then remove air at top bolt to master cylinder. The to pump through to remove air.

Or

Attach a huge vacuum pump to the caliper bleed nipple and suck the stuff from the master with leaking air from the nipple and loads of bubbles with not knowing if its working.

Or

A better well thought out solution that works correctly with the right tools and following a correct procedure.

If you have "the" method or just a tip to help on the way I would be grateful to have your input and guide me on this sticky, leaky path.
 
Reverse fill is the quickest. Standard bleeding for the front is fill the MC and start bleeding from the caliper furthest away (left) once no air there do the right. It helps to have the bike on the side stand and handlebars full left so the MC is the highest point of the system. If you can't get a firm brake on the first attempt, just leave on side stand with bars full left. Sometimes the last bit of air will go to the MC on its own. It helps to have two people do do this unless you have very long arms.
 
I have tried filling master cylinder and bleeding furthest caliper. However, in my case the fluid will not travel into the brake line from the MC. If I remove the pipe fitting and put my finger over the exit hole and pump the leaver, fluid is forthcoming. However, with the line attached, the easy compress/expansion of the air in the line seems to not allow the fluid to pass through the MC valve.
 
NPS said:
I have tried filling master cylinder and bleeding furthest caliper. However, in my case the fluid will not travel into the brake line from the MC. If I remove the pipe fitting and put my finger over the exit hole and pump the leaver, fluid is forthcoming. However, with the line attached, the easy compress/expansion of the air in the line seems to not allow the fluid to pass through the MC valve.
Click to expand...


I'm pretty sure you are closing the bleeder after you squeeze the MC. If not that could be your problem as the MC seems to be working. If you try the vacuum pump method, I find it helps to wrap the bleeder threads with Teflon tape. If you do that, be sure to not cover the bleeder hole.
 
NPS said:
I have tried filling master cylinder and bleeding furthest caliper. However, in my case the fluid will not travel into the brake line from the MC. If I remove the pipe fitting and put my finger over the exit hole and pump the leaver, fluid is forthcoming. However, with the line attached, the easy compress/expansion of the air in the line seems to not allow the fluid to pass through the MC valve.
Click to expand...

That is common with new lines. The MC has a hard time picking up the fluid when the line is empty as it tends to dump air back in the cylinder on the return stroke. If you have a vacuum bleeder, you can suck a little from the caliper bleeder while you are pumping the MC. That is usually enough for the MC to start pumping and then you can bleed the entire line. Just need to get fluid in the hose on the other end of the MC. Other method is to use a syringe to pull a vacuum on the line from the bleeder and then start pumping. That is usually enough to get things flowing.
 
Thanks canuck. I ordered a vacuum bleeder to suck the fluid through while pumping MC.
Thanks John. I'm definitely doing it in the correct order also with PTFE tape. Learnt that a few years ago. When you open the bleed, the air bubbles that come out can be from the bleed nipple thread unless sealed if the bleed tube is lower and placing a suction on the bleed nipple.
 
I tried the vacuum pump today. After several minutes and top ups to the master I realised there was air leak. Can only be MC seals. I will try and get some. 16mm Brembo Pc16. Bremobo dont sell kits and expect you to but a new master cylinder. I see KTM bikes have Brembo cylinder kits. Need to find one that matches.
 
NPS said:
I tried the vacuum pump today. After several minutes and top ups to the master I realised there was air leak. Can only be MC seals. I will try and get some. 16mm Brembo Pc16. Bremobo dont sell kits and expect you to but a new master cylinder. I see KTM bikes have Brembo cylinder kits. Need to find one that matches.
Click to expand...


I've not had much luck with the new master cylinder rebuild kits. The entire master cylinder isn't much more than the kit and will save trouble. If you get the kit and it doesn't work, you still have to by a new master.
 
I took the master cylinder apart. There was rust contamination. After cleaning the cylinder surface it does not looked scored. The seals looked ok too. I spent an hour or two trying to find a seal kit from KTM or other, but no luck. I realise I may have to replace the who cylinder but I'm at the end of my budget now. I decided to clean and reassemble without the eternal plastic bellows type cover as it was damaged. Added some external grease to catch and deflect water from entering the end of the cylinder. A temporary measure to get the bike on the road. There was a problem with the rust and drawing in air and the cleaning made it work as normal without replacing the seals.

I successfully bled both front brakes and the feed is hard very soon on the handlebar lever travel. But note to self to sort this out long term in a few months.
 
NPS said:
I took the master cylinder apart. There was rust contamination. After cleaning the cylinder surface it does not looked scored. The seals looked ok too. I spent an hour or two trying to find a seal kit from KTM or other, but no luck. I realise I may have to replace the who cylinder but I'm at the end of my budget now. I decided to clean and reassemble without the eternal plastic bellows type cover as it was damaged. Added some external grease to catch and deflect water from entering the end of the cylinder. A temporary measure to get the bike on the road. There was a problem with the rust and drawing in air and the cleaning made it work as normal without replacing the seals.

I successfully bled both front brakes and the feed is hard very soon on the handlebar lever travel. But note to self to sort this out long term in a few months.
Click to expand...


Make a complete repair as soon as possible. Brakes are a necessity. You life depends on them.
 
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