Strange bleeding issue

On my VF500 I just totally rebuilt both calipers and the master cylinder. I cleaned out the 25-yr old gunk that settled in the calipers and m/c. I cleaned and greased all bushings, put the banjo bolts on with 10ft-lbs of torque, and filledup the master cylinder.

After quite a bit of lever pumping, fluid finally came out of the calipers. Then, the lever got a bit stiff, but only when it is pulled all the way to the grip, and only after a *lot* of pumping.

No more air is coming out of the caliper bleeders, and I felt the hoses with my hands while pumping and they didnt seem like they were expanding.

I also noticed that when I break the bleeder valve it takes about 25 pumps to get the pressure back up in the lever/line.

The bike is 25yrs old, and they don't make new hoses.

Can someone help me?

 

I've had to loosen the line at the MC before and get it to bleed and then bleed the calipers. Put towels around the MC it gets messy, kinda like cars you bench bleed the master before installing.

 

Is that why I have to pump so many times after bleeding with just one opening of the bleeder screw?

 

I would double check all the banjos. Had a similar issue when I went SS lines, torque is your friend.

 

Do you have a vacuum pump for this? It might be a helpful tool this. They are only about $30 (maybe even cheaper at Harbor Freight) and I believe that some AutoZone's will loan them as well.

You've either got an air bubble somewhere or bad lines. Concerning the air bubble..which is why I mention the vacuum pump... a friend of mine that has been a bike mechanic and raced for 20 years or so taught me a neat trick. Using the vacuum pump you can push fluid into the system from the bottom up. I haven't had a chance to try it yet but he swears by it. Captb's recommendation of loosening the line at the MC is also spot on. Sometimes a bubble can get trapped there and be difficult to remove.

Concerning the brake lines, you need to check out Spiegler. Even if they don't stock them, they can make any line you would ever need. Simply take measurements, choose your fittings, and place your order. They are excellent quality lines too.

Spiegler Performance Parts

 

How big is the tiny hole for the return path for the fluid? The lever returns to full out slowly and it seems the hole is still filled up with some sludge.

I will give the Spiegel's a try. I read that older bikes have bad lines that can expand. Wouldn't I be able to feel it, though?

 

Fluid return hole must be clear and open.....could cause brakes to stick on if blocked.

be sure to leave some air space above fluid in MC

 

Ok, I cleared the hole out, replaced the brake lines with new ones, filled with fluid.

Got both calipers running clear, loosened the banjo bolt and air came out at first, then cleared that out.

Still was spongy, kept bleeding top and bottom, checked for leaks, but couldn't get sponginess out of the lever.

So I took the lever off, grabbed the piston with a pair of needle-nose pliers, pulled it back quickly (it went back slowly otherwise), and the smallest of bubbles came out. I did this for about 15min and bubbles still coming out. Though in VERY small amounts.

I suspect that after rebuilding the master cylinder there is still air down around the plunger by the lever and not by the banjo bolt.

Is there an easy way to flush out the plunger passageway on the m/c?

 

remove mc from handlebar and hold it at angle with banjo pointing up while bleeding mc

also remove each caliper, tap lines and caliper with rubber hammer to break up and free small bubbles, then raise caliper as high as possible while squeezing lever and briefly opening bleed screw

sometimes air bubbles will remove themselves by traveling up back to the mc

 

Good points. I angled the mc up, down, left, right, while pumping the lever. No bubbles got out. I tapped the m/c with the wood-end of a hammer b/c sharp vibrations usually free the bubbles up.

I also put the brakes on quite a bit on test rides to heat up the fluid and get vibration in the system so as to get some bubbles up.

I've never had such a hard time bleeding a system, but again i've never done a bike this old.

 

Seems like you know what you're doing and have covered all the bases, so maybe those old brake lines are expanding under pressure and feeling mushy ??

 

was i supposed to fill the plunger first with brake fluid in the m/c before reassembling it?

I actually put new lines on, too (well, I retrofitted new ones from a new 600RR I put galfers on).

it is almost as mushy as before I rebuilt everything.

 

Use pliers to firmly squeeze the line just after the mc.

does the lever hold firm or sink down ??

hold pressure, then squeeze and hold line, then release lever and release pliers......

it's always helpful to bench-bleed mc first b4 attaching it to system.

 

Those lines from the CBR might be somewhat bad as well. Grab one of the rubber lines with your hand and actuate the brakes with the other. You will probably be able to feel the line expand in your hand. Mine do and I know that is where my sponginess comes from. However I also still have more than enough braking power to lock up the front so I haven't ordered new ones yet. I'll be snagging my from Spiegler over the winter when I get a bunch of other stuff and do some seasonal maintenance.

 

Do you mean watch the lever without pulling it in? Or squeeze the lever mid-way and see what happens when I put pliers on the line?

What am I looking for here?



How would I bench-bleed the mc?