Bleeding at the upper banjo bolt

[J_C]

I cannot describe how much this has helped me. The only reason I knew about it was because I read about it in an old old thread that's recently been resurrected (regarding master cylinder ratios). So I thought I'd share the knowledge (I so rarely have it to share! :-D )

So I had endless problems with my brakes. I replaced the old lines with new OEM lines (I know, I know), rebuilt the master with oem piston, bled nearly half a bottle through at various times. I tried the screwdriver trick and the zip tie over night trick. I recently installed one of those ebay 14mm master cylinders and still could feel sponginess. I knew there had to be air in the system, even after profusely bleeding. This is what finally worked for me:

I pumped up the pressure in the system, and zip tied the lever down. I started at the pistons and, using my fingers, gave many quick taps to the lines. I worked all the way up to the top banjo bolt. I left it over night.

The next morning, I went down and clipped the zip tie. It felt better, but still spongy. I used my bike cover to cover the entire bike except for the right handlebar. I placed a rag around the upper banjo bolt. Once I pumped up the pressure in the system, I held down the lever as hard as I could and cracked the banjo bolt. *PFFFFFFFTTTTT!!!!* A fine mist and a puff of air came shooting out.

I put on goggles this time, and did it again. Another puff of air. I did it until all I got was a squirt of liquid.

I thought I'd try one more time. I zip tied and tapped, and left it over night. The next morning I clipped it, it still felt good, but figured what the heck. I cracked again, and *PFFFFFFTTTT!!!* another mist came out. I cracked it another two times until I was sure all was coming out was a thin stream of fluid, no air.

The results are incredible. Now we're talking about true two fingered breaking. I feel it engaging very shortly after the switch is triggered, and it is a progressive pressure I feel on the lever. I wasn't able to take the bike out today, but I can't wait until next week when I'm back from my business trip to see if I can make the front tire bark. I suspect I finally might be able to.

[chef1366]

Good news. The mystery is solved! I'll take your old M/C. :-D

[J_C]

Yeah, who woulda guessed. Bastard air.

The old MCs not from from a gs1100, it's actually off of an 850L I think? It does, however, have a new switch assembly (wiring cut), new resevoir, new o ring, new piston and associated parts.

[terbang]

I actually have a banjo bolt on my master cylinder that has a bleed nipple on it. Very helpful. Picked it up in Aussie somewhere.

[49er]

I cannot describe how much this has helped me. The only reason I knew about it was because I read about it in an old old thread that's recently been resurrected (regarding master cylinder ratios). So I thought I'd share the knowledge (I so rarely have it to share! :-D )

So I had endless problems with my brakes. I replaced the old lines with new OEM lines (I know, I know), rebuilt the master with oem piston, bled nearly half a bottle through at various times. I tried the screwdriver trick and the zip tie over night trick. I recently installed one of those ebay 14mm master cylinders and still could feel sponginess. I knew there had to be air in the system, even after profusely bleeding. This is what finally worked for me:

I pumped up the pressure in the system, and zip tied the lever down. I started at the pistons and, using my fingers, gave many quick taps to the lines. I worked all the way up to the top banjo bolt. I left it over night.

The next morning, I went down and clipped the zip tie. It felt better, but still spongy. I used my bike cover to cover the entire bike except for the right handlebar. I placed a rag around the upper banjo bolt. Once I pumped up the pressure in the system, I held down the lever as hard as I could and cracked the banjo bolt. *PFFFFFFFTTTTT!!!!* A fine mist and a puff of air came shooting out.

I put on goggles this time, and did it again. Another puff of air. I did it until all I got was a squirt of liquid.

I thought I'd try one more time. I zip tied and tapped, and left it over night. The next morning I clipped it, it still felt good, but figured what the heck. I cracked again, and *PFFFFFFTTTT!!!* another mist came out. I cracked it another two times until I was sure all was coming out was a thin stream of fluid, no air.

The results are incredible. Now we're talking about true two fingered breaking. I feel it engaging very shortly after the switch is triggered, and it is a progressive pressure I feel on the lever. I wasn't able to take the bike out today, but I can't wait until next week when I'm back from my business trip to see if I can make the front tire bark. I suspect I finally might be able to.

The quickest method I've found is fill the master cylinder and then work backwards from the calipers.
Fill a squeeze bottle with brake fluid and attach a clear plastic hose that will fit tightly over the caliper bleeder. Now loosen the master cylinder banjo bolt and squeeze the bottle until the air and fluid is forced through the lines and out of the banjo fitting. Now close the bleeder and transfer the hose to the other caliper and repeat the process. Once you have continuous air free fluid oozing from the banjo fitting, tighten the caliper bleeder and the banjo fitting. You now have the system clear of air from the calipers to the master cylinder banjo. Now pressurise the system with the brake lever and release the banjo intil any air is expelled between the master cylinder piston and the banjo fitting. Voila!! Enjoy your new brakes.

[chef1366]

The quickest method I've found is fill the master cylinder and then work backwards from the calipers.
Fill a squeeze bottle with brake fluid and attach a clear plastic hose that will fit tightly over the caliper bleeder. Now loosen the master cylinder banjo bolt and squeeze the bottle until the air and fluid is forced through the lines and out of the banjo fitting. Now close the bleeder and transfer the hose to the other caliper and repeat the process. Once you have continuous air free fluid oozing from the banjo fitting, tighten the caliper bleeder and the banjo fitting. You now have the system clear of air from the calipers to the master cylinder banjo. Now pressurise the system with the brake lever and release the banjo intil any air is expelled between the master cylinder piston and the banjo fitting. Voila!! Enjoy your new brakes.

I'm going to try that some day!

[49er]

I'm going to try that some day!

Bill, it's not rocket science, but it works.

The only time I have ever been caught out was with a M/C that had the small return hole completely blocked. It had sat for some time prior to me fitting it to the bike. Air got trapped in the piston bore and was difficult to move until I realised what was causing the problem.

[salty_monk]

I just put a hose on the caliper bleed nipple & suck it through....

Dan

[PAULYBOY]

I just put a hose on the caliper bleed nipple & suck it through....

Dan

Yeah, works great with a Mityvac and the appropriate little jar and attachment hose. You can also make an anti backflow bleeder out of hose and a Mercedes one way vac valve, part number 123-800-00-78. These work great by attaching to the hose, hooking the hose to the bleeder and cracking it open. As you squeeze the lever, air comes out, but the one way valve keeps the stuff from going back in through the out door. $10 for the valve isn't too bad.

[J_C]

Believe me, I mity vac'd too. But no matter how much I sucked through, I couldn't get rid of the air. I assume because it was all up at the banjo. I even tried mity vacing at the master cylinder, no good.

It sounds like it might be messy, but if you have ANY sponginess, give the banjo bleed a shot. Only a small stream of fluid will come out. Just cover everything up first.

[seuadr]

Believe me, I mity vac'd too. But no matter how much I sucked through, I couldn't get rid of the air. I assume because it was all up at the banjo. I even tried mity vacing at the master cylinder, no good.

It sounds like it might be messy, but if you have ANY sponginess, give the banjo bleed a shot. Only a small stream of fluid will come out. Just cover everything up first.

yep. i always start and finish a bleed with the banjo at the master. first that one, then the rail that splits''em down to both front calipers, then each caliper, then each anti dive. then i bounce the paddle for a bit, releasing it hard to shake the lines, the bleed the rail again, then the master banjo again. works like a charm.

[J_C]

I assume you first disconnect the rail from the frame? Then you just tilt it and do the side now elevated?

[49er]

I assume you first disconnect the rail from the frame? Then you just tilt it and do the side now elevated?

When you pressurise the system from the calipers back to the M/C banjo, the air always takes the easiest way out, which is upwards. I have never ended up with air trapped in the rail (tee piece) using this method.

Using a squeeze bottle is quicker than individual pumps on the brake lever. Also, you're not trying to force air in the lines downwards.

[seuadr]

When you pressurise the system from the calipers back to the M/C banjo, the air always takes the easiest way out, which is upwards. I have never ended up with air trapped in the rail (tee piece) using this method.

Using a squeeze bottle is quicker than individual pumps on the brake lever. Also, you're not trying to force air in the lines downwards.

yep. don't have to detach it from the frame, the air is going to be looking for somewhere to go. usually the first time, i get a little pfff of air, the second time, nothing. but it only takes an extra second to make sure it's fluid and not air at the rail.

[bubba]

I just finished replacing my old lines with the SS ones from Z1. I ran into the same problem. After several bleedings at the screws, I finally got some pressure and did the zip tie trick and tapping the calipers and lines. Next day I had decent pressure. Repeated the process and a day later the lever was high and hard. Just for grins I cracked the banjo bolt at the m/c and all I got was fluid. This was a huge help!!!! The Clymer manual doesn't even mention any of this. Had I depended on it alone I would have pulled out what is left of my hair by now. The Clymer is a big help, but the experience of the folks on this site is MUCH more valuable.