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Front Brake Bleeding

Posted: Thu Aug 25, 2005 12:27 pm
by KillerB
I just replaced my original brake and clutch lines with stainless and am having a problem bleeding the front lines. The clutch and rear were no problem, but I can't seem to get any pressure on the front :confused: . Does anyone have any tips or suggestions?

Regards, B

Posted: Thu Aug 25, 2005 2:00 pm
by DesmoDog
It's been a long time since I've done this to my 907, but I seem to remember having to lean the bike over so the M/C was the highest point in the system before it would bleed properly.

With the bike sitting on the centerstand and the front wheel straight forward, I think the banjo bolt is the highest point? So what I did is turn the wheel and maybe even lean the bike so the master cylinder is more or less level. Then if you slowly squeeze the lever with the reservoir cap off, you will see bubbles. If you squeeze the lever too fast, you can shoot brake fluid up and out of the M/C though, so be careful. (I think on some bikes there is a metal guard in there to keep this from happening?)

Anyway, that's what I remember helping. But in all seriousness I might be thinking about my 900ss! Pretty sure it was the 907 though...

Posted: Thu Aug 25, 2005 5:20 pm
by jcslocum
A vacuum bleeder will do it best. Try to borrow 1 if you can or you can make an effective one with a small coffee can and some tubing.

To make the coffee can bleeder:

You need clear tubing that will fit snug over the bleeder nipple, about 2 feet will do the trick. Poke 2 holes (slightly small than the tubing) into the coffee can top. about 3" apart. Feed the tubing into one of the holes until it's about 1" from the bottom. You can put some sealer around the hose if you made the hole to big.

This job is done best with a helper to keep the reservior topped off during the bleeding.

You are now ready to "let it bleed", Remove both bleeders from the caliper and apply some anti-sieze just to the threaded portion. DO NOT get any on the taper section, it will contaminate the fluid if you do. The A-S creates a seal for better bleeding and keeps them from siezing up later. Screw the bleeder in hand tight.

Slip the proper wrench over the bleeder and push the hose over the nipple. Now sneak inside and grab that vacuum cleaner, quiet or the missus will hear you!

Fill up the res and start up the vacuum. Place the vacuum hose over the 2nd hole in the top of can and open the bleeder with the wrench. Make sure that your able bodied assistant keeps the reservior full. Once the fluid begins to run clear of bubbles, close the fitting tight and shift to the other side. Do both sides this way twice. The second time you should get no bubbles...hopefully.

Good luck!

Posted: Thu Aug 25, 2005 5:28 pm
by KillerB
Thanks for the response, guys. I will give it a go tonight and let you know how I make out.

Regards, B

P.S. I like your animated Jolly Roger.

Posted: Fri Aug 26, 2005 1:11 pm
by KillerB
I followed your tip, DesmoDog, by putting the bike on the side stand. About two minutes of gentle squeezing and all the air bubbles were gone :thumbup: . Thank-you. The Queen B spent about an hour the night before squeezing the lever while I worked on the bleed valves, so she just about killed me when I told her how easy it went.
jcslocum, that coffee can vacuum pump is going into the old shop memory book for future use.

Regards, B

Posted: Fri Aug 26, 2005 3:41 pm
by DesmoDog
I'm glad it worked out! :thumbup: The more I thought about it, the more sure I was that I had to do this on my 907 and not my 900. Mainly because I remembered a little episode where this happened to me.

For me it was the clutch I was having trouble with. I bled it a bunch of times. Then I decided the master cylinder had gone bad and rebuilt that (after an ordeal trying to get the correct parts, but that's another story). Still no good. Then as I was contemplating rebuilding the slave cylinder, I remembered what I had to do the last time I changed fluid in the clutch. D'oh!

I tipped the bike, slowly pumped the lever... problem solved.

I later bled the clutch on my 900ss like this when I had to rebuild the slave cylinder and toasted the banjo bolt in the process. It was a holiday weekend so no shop was open. The only replacement bolt I had didn't have a bleeder on it, but I wanted to ride, so I figured what the heck? It worked fine, but I wonder what the next owner thought when he went to change the fluid and couldn't find a bleeder anywhere???? :confused: