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Brakes don't want to bleed !!!

  • Thread starter Thread starter Unclesol
  • Start date Start date
U

Unclesol

Guest
I just put a set of stainless brake lines on my 83 750 ES, and disconnected the anti-dive system. So, this should be simple, right? However, after close to an hour of bleeding (only getting small amounts of fluid through the lines, starting with the left (furthest from the master cylinder) caliper), I am still not getting any lever back. In other words, it is still going to the bars.
The system worked perfectly before installing the lines, and I expected an even simpler system (fewer places for air to be trapped) to work much better, in combination with new progressive fork springs to compensate for removing the anti-dive. But it's not !!!!!!!
Any suggestions? Thanks.
 
You have a bubble in the master cylinder - which can be a bear to get out. I had a similar problem with my old 450 and had to take the master off the bike and feed fluid in through the outlet port to get the damn thing to prime properly before it would pump the way it's supose to.
 
So, I take it off the bike and stand it on end so the outlet is up, and then force fluid back into the master between squeezes of the lever? If this is correct, I guess I need to leave some space in the reservoir?
Thanks for the help!
 
Unclesol said:
I just put a set of stainless brake lines on my 83 750 ES, and disconnected the anti-dive system. So, this should be simple, right? However, after close to an hour of bleeding (only getting small amounts of fluid through the lines, starting with the left (furthest from the master cylinder) caliper), I am still not getting any lever back. In other words, it is still going to the bars.
The system worked perfectly before installing the lines, and I expected an even simpler system (fewer places for air to be trapped) to work much better, in combination with new progressive fork springs to compensate for removing the anti-dive. But it's not !!!!!!!
Any suggestions? Thanks.
Click to expand...

It's common to take HOURS to sucessfully bleed front brakes. When I have a completely set of "dry" lines. I crack the caliper bleeder screws, and fill the M/C, and just be patient and let "gravity" do it's thing. With this method, it's CRITICAL you don't let the M/C go dry! This method takes severall hours, but when done right, you will only need about 5 min of traditional "pump-n-bleed" method.
 
I'm guessing this would include a tie-wrap to hold the lever in and allow fluid to pass out of the MC and down to the calipers?
 
Tap

Tap

Years ago, I learned a trick from a HD mechanic and it works great. With your master cylinder filled and the cover off, tap rapidly on the lever with your fingers. You don't have to do it hard...just hard enough to reach resistance. Do it for a couple of minutes and the bubbles will come to the surface.

I've never had it fail and it usually doesn't take very long at all. Good luck! :-D
 
Thanks Chucky. I hope all the noise from the garage tonight won't bother the neighbours. I appreciate the help!
 
Tap, bang, force fluid in backwards, pray to a pagan god...yes, it's a bitch getting the air out. Once you get that bad boy primed though, you can pump the fluid on through to get the rest of the air out.

Good luck.

Ed
 
Last edited:
Your brake lever doesn't push the piston all the way into the port of the M/C. First remove the brake light switch and then the brake lever. With the M/C cover off push the piston all the way in with a screw driver or something similar. I used the old piston since I was rebuilding it. When I pushed it all the way in I got one big bubble to surface and I was on my way. This was after an hour or so of pumping a dead dead lever and cussing out loud. (I know I'm gonna hear it after that last sentence):shock:
 
Thanks for the tip! I'll let you know if it stops my cussing (there has been plenty so far...)
 
If all else fails...
put a crap load of rags and plastic all over the bike to save the paint from getting fluid on it, remove the line off the master and put a small bucket under the outlet port, with your finger over the outlet port of the master cylinder port squeeze the brake lever, hold it, let finger off the outlet, put finger back over the outlet port and repeat till fluid comes out then hold your finger over the outlet port and get the banjo bolt and line ready to quickly screw back in the master cylinder port and finish bleeding the rest of the system. don't forget to add brake fluid or you'll be doing it AGAIN.
 
...and the winner is...

...and the winner is...

Chef !
Thanks for the tip. It worked like a charm! I'll be thinking of you the next time I come to a nice, smooth, powerful stop.

Ian
 
There is also a real slick tool called a "mighty-vac" Its a small pump actuated vaccume tool that you connect to the lower bleed screws and simply pump away. It draws fluid down through all the lines. Problem is the tool is $30. Me personally I'm too cheap and stupid. I would rather waste 6 hours on a sunny Sunday, than go spend $30 and be done in 10 min.
 
Road_Clam said:
Me personally I'm too cheap and stupid. I would rather waste 6 hours on a sunny Sunday, than go spend $30 and be done in 10 min.
Click to expand...

I have a Mighty-Vac, you can indeed bleed the brakes in 10 mins. No mess either. Life is too short to waste 6 hours bleeding brakes. :(
 
Unfortunately, the Mighty-Vac is made out of plastic and mine just cracked in half from age - less than 10 years old. Yea I know, 10 years is a long time. But I have tons of tools that are three times that old and are like new.
 
vacuum

vacuum

After rebuilding the front master cylinder for my 1980 gs550, I also found it to be impossible to get pressure in the lines. I found a great trick by accident: I had a hand pumped syphon thingy and I hooked the "suck" end to the bleeder valve. Next I pumped it until there was a mild vacuum in the pump, then I opened the bleed valve and closed it again after about 2 seconds. I repeated this a few more times and when I got back on the brake lever... WOW! Like magic, I finally had brake pressure! I figure by sucking the fluid thru the lines instead of just pushing it the bubbles get sucked right out. Good luck!
 
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