Still can't bleed front brakes after adding NEW Master

I'm stumped.

I replaced the double lines with one single steel braded line. Rebuilt the caliper, and installed a brand new Master Cylinder assembly from MikesXS.com

I still can't get the brakes to pressurize. I put three resevoirs through, no more are coming out of the bleeder line, but there's still no pressure.

The only thing I can think of is that the new line has a wider inner diameter then the old one. I checked around, talked to some hydraulic specialists that I know, and they said the size of the pipe should matter. It just means your just carrying more fluid in the line then a smaller one.

What else can I look at?

 

If you meant to write:

"they said the size of the pipe shouldn't matter."

You have been told right!
Internal diameter of hose doesn't matter.

Try to shake hoses or tap on them lightly with spanner or something. If you see bubbles coming out in oil tank there is still air in line.

That will help to release trapped air.

 

Yup, that's what I mean to say.

Oh man, I've tried everything. My hands are killing me from pumping that brake line.

 

Wrap a bungee cord around the brake lever and let it sit overnight with the lever compressed and the resevoir. Then try in the morning. This allows the air to float up to the resevoir and escape. If this doesn't work then find someone with a Mity-Vac. Harbour Freight has a similar brand for about $20.

 

make sure your brake cable is properly adjusted and you are getting full travel of the piston

 

Totally forgot we had a brake bleeder pump in the shop.

Hooked it up, put and rubber band around the handle holding it down, hooked up the pump the bleeder value, opened it... and I've got to pump like mad just to get a little bit of oil out. Something's not right.

 

Still stumped.

Using the brake pump, I got all the air out, it's perfect. Still no pressure. Could there be something wrong with the caliper? To test this, I took the line off and put compressed air to the caliper. It closed quickly and held the pressure.

I have no idea now... It's driving me insane. Help, anybody.

 

With the caliper off, & disconnected, does the brake line push oil when you squeeze the lever? Is it a strong pressure? See if you can adapt a pressure gauge to it for a measurement. You've got to have pressure on that line.

Now, the caliper - off the bike, cyl back in all the way. Fill the caliper reservoir completely. Put your air tool on it - Does it slam out? Easily?

Again, caliper off the bike, fill the reservoir with the cylinder OUT. Closed bleeder, tap on it with a plastic mallet to dislodge all the bubbles inside.
Fill it until your sure only fluid is inside.

Now make sure the lever reservoir is full, plug up the hose end, put the cap back on the full reservoir.
Now pull the hose plug, connect the hose & caliper leaving it a bit loose while you allow fluid to escape the fitting as you push the caliper cyl. slowly back in about half way or less as you tighten the fitting.
Open the lever reservoir lid and slowly push the caliper cyl back in, while watching the oil rise in the cup. Siphon off what you need to keep from spilling over.
Close the lid on the lever reservoir cup & test the system - Should have easy movement of the caliper cyl.
Now clean & mount that caliper with some pads, and you should have solid brakes.

 

Dan,

Thanks for the ideas. I'll try those out tomorrow. It's a new line, but ya never know. it could have a small air leak, although the entire line is bone dry with no signs of fluid. With your info, my guess is there is a big air pocket in the caliper. I'll take it off tomorrow and fill it complete.

Thanks,

 

I assume the first post above meant you pumped 3 master cyl reservoirs of brake fluid down the line or it had to got someplace??? But your last post said the line is bone dry which is confusing, where did the fluid go, maybe it needed more.

When I replaced my dual brake system with SS lines I did have one heck of a time getting the thing to pressurize.

First I mounted the calipers and filled them and the connecting section of brake line via the bleed screw and a syringe.
I connected those lines up with a full reservoir and figured it would go real fast!
It didn't, I found out the master cyl wasn’t pumping, I had to pull a vacuum on the output line and pump before it started to pump fluid. Then it took a whole bottle of brake fluid and a long amount of pumping before I got the system to work.
On my bike, by accident I located a small leak on one of the brake line connections, got that fixed and bingo brakes worked.

I would check each joint in your system with a clean tissue, wipe the joint if the tissue gets wet, you got a leak and the system won't pressurize.

 

Someone forget to put seals in that new master cylinder by any chance?

 

Nick,

Sorry, by bone dry, I meant the outside. No leaks found.

I'm going to get a syringe and a new bottle of brake fluid tomorrow and start again. The master cylinder has lots of pressure, that's what's making it so strange.

 

I can't imagine how a Brake Fluid Leak could possible go unnoticed on a Motorcycle.

Get a Syringe.
Bulb type. The kind for Ears.
Remove the Bleed Screw.
Crack the Banjo Bolt on the Caliper and use the Syringe to Fill-up the Caliper.
Tighten the Banjo.
Leave the Bleed Screw out and put you Thumb over it.
Have an assistant work the Brake Lever.
They Pull the Lever ... You remove your Thumb.
You Cover the Bleed Hole Tight ... They release the Lever.

This should have Fluid moving out of the Master Cylinder in just a few repetitions.

If fluid isn't coming-out after 8 repetitions and there's no pumping "Feeling" happening at the Master.

The Master's is vacuum-locked or Bad.

 

Make sure the small secondary hole in the master cylinder is not plugged.

I also had a hard time bleeding my new braided lines. I found that filling the master cylinder up completely, then putting the cap on before pumping it up solved the problem. immediately.

 

I had a similar problem a few years back with all original brake parts. I couldn't get it to pressurize until I put the cap on either. Pita having to take the cap on and off to top up the resevoir, but it got the system working.

 

Now, I'm even more stumped. I pulled the caliper off and pushed oil through the bleeder up into the master cylinder. A lot of air came out. Great!

So now, if you pull the brake handle, the piston does move. Maybe 2 or 3 mm. Not enough to close down on the disc. I wonder if maybe MikeXS sent me the wrong one. Doesn't seem like there is enough movement of fluid to push the piston out enough to grab the disc.

 

Nope, Mike sent me the right one. 13mm bore, same as stock. Ahhhh, can't figure this one out.

 

I recently went with the braided s/s line and had a similar problem in not getting my system to pressurize.
The problem was a lack of travel on the brake lever adjustor screw. Once I removed the lever and operated the brake plunger manually, the system pressurized immediately.
And the difference in brake lever feel is incredible. With the 2, old rubber lines, the brake lever adjustor was about 95% IN (no more adjustment possible), and the feel was somewhat spongy or soft. With the braided line, the adjustor is about 95% OUT, and the feel is FIRM!

 

Hmm, mine is adjusted all the way in!

 

Let's hope you've found your problem!!
More lever travel was my first thought before I read the next post by Dispatcher.

I'm going to put braided hose & a fresh Master on my bike soon, so it's great to see this discussion.
Dan