Weak Front Brakes, Any Advice...Idea's?

[Steve K (IA)]

So, as I am backing the bike out of the garage for the first time this year, I pull the front brake lever and it comes all the way to the grip and I didn't stop.  Put the kickstand down right there and proceeded to bleed the front brakes.  That helped very little.  So I thought a master cylinder rebuild was in order.  After the rebuild, it works a little better, but still very spongy. 
I have Speed Bleeders on the bike and I own a Mityvac.  When I bled the brakes the first time, I used the Speed Bleeders.  After the master cylinder rebuild, I used the Mityvac.  It is like there is still some air in the system, but I sucked more than a bottle of fluid through both calipers.
I am at a loss as to what to look for next, any thoughts?   ???

[9Ball]

One trick I've found is to install the regular bleeder nipple, then using a syringe and tubing force brake fluid up through the system.  Make sure there is adequate room in the M/C to accept the amount of brake fluid you inject.  Just crack open the bleeder enough to allow fluid to flow and close it while maintaining slight pressure on the syringe...this prevents introducing air into the system.

This normally dislodges the bubbles that collect at the fittings and at the M/C connection.  Once the bubbles stop, disconnect the tubing and re- install the speedbleeder.  If you do this quickly enough the head pressure will prevent air for entering and allow a slight amount of fluid to drain from the system (I hold a rag to catch the leakage).

It's a lot easier to force air upwards than down through the whole system.  This method also conserves brake fluid...

Good luck.  This has worked well for me for both stubborn air bubbles in both new brake lines and old lines.

[Thunderbolt]

Worked for me on the clutch once, tie the lever to the bars overnight or for a day or so.  This lets the air work it's way to the reservoir and out.

[Ricky-D]

There have been, on occasion, reports of stubborn bubbles in the gallery where the single line from the master cylinder connect to the split line, under the lower fork brace. Standing the bike upright will help to eliminate this problem with bleeding.

Another trouble area is with the master cylinder, where a small amount of air remains regardless of bleeding attempts.  Loosening the banjo and letting brake fluid flow sometimes helps to eliminate this particular problem.

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[PhredValk]

Have you checked your pads? Brass on steel isn't going to stop you much, and they don't always make a lot of noise...
Also tie down the brake lever and check every inch of the brake lines. Any bulge or bubbling of the lines is a sign of disaster.
Fred.

[PAVALKER]

And you might as well check rotor thickness in addition to pad thickness..... 

[Steve K (IA)]

Guys, thanks for the ideas.  I have/had a large syringe, I couldn't find it so I tied the brake lever to the handlebar.  That seems to have worked.  It doesn't have as much travel as it did before, and feels firmer.  I haven't been out for a test ride yet, but I expect it to be much better.

[Thunderbolt]

Thanks for posting your results.  At least we know for next time.  Glad it worked for you.

[John Schmidt]

An additional note; if you haven't already done so, it's time to replace the OEM hoses with SS hoses. Even with good brakes, they make them feel more solid, they don't expand like the OEM hoses with a few years behind them.

[gordonv]

If it doesn't continue to improve, it almost sounded like the bleed valve was not sealed and air was getting back in the line.

[Steve K (IA)]

If it doesn't continue to improve, it almost sounded like the bleed valve was not sealed and air was getting back in the line.

It probably wouldn't hurt to get some thread sealer from Speed Bleeder and reapply the stuff to the treads. 

[Steve K (IA)]

Well, got my I/S out for a ride and my front brakes work great.  The "tie the lever to the hand grip" tip worked.     Going to order some thread sealant and redo all the Speed Bleeders.  Two Valks = 8 bleeder valves.