Bleeding the Brakes

Gpaws1968

XS650 Enthusiast
Messages
64
Reaction score
52
Points
18
Location
California
So, I did a full rebuild on my front brake, I got it all assembled and now I'm starting to bleed the system and it's taking forever to get the fluid through the lines, is there a better way than pumping the lever?

1981 XS 650
 
Pumping the lever does work.
Keep the master cylinder level.
Tap on it lightly with something to help the last bubbles rise out.
Be patient and feel the fluid fill the spaces.
Bleed the calipers when that feel is good
🤞
 
if you have a compressor, get a vacuum bleeder from Harbor Freight.
I just finished rebuilding calipers and putting in new pads and steel braded brake line on my 82 XJ650.
Bleeding takes less than 5 minutes. with that thing, I bleed more than I have to since a bottle of brake fluid is enough to do several bikes worth and I toss it after doing one bike.

They also make pump vacuum bleeders but never used one.
 
I recently rebuilt the front brake on my 77 650 too. I was surprised how difficult it was to bleed given it has only a single piston caliper. A bit less sophisticated than above, I used a plastic syringe and a short piece of plastic tube to suck the fluid from the bleed nipple. Draw the fluid though until the bubbles are gone. Takes a few attempts but it works.
 
IA bit less sophisticated than above, I used a plastic syringe and a short piece of plastic tube to suck the fluid from the bleed nipple. Draw the fluid though until the bubbles are gone. Takes a few attempts but it works.
A variation on the above is to reverse bleed, i.e. push the fluid back up into the reservoir. That way you are pushing the air upwards rather than trying to pull it down. Source some silicon hose for the syringe as this is flexible and gives a good seal over the bleed nipple.
You do need to keep an eye on the reservoir to make sure it doesn't overflow - some cling film over paint is a good precaution.
When done tie the lever back over night to remove any remaining air.

One other thing to do is to put a couple of wraps of PTFE tape around the bleed nipple thread to ensure you aren't pulling in air. via the threads.
 
A variation on the above is to reverse bleed, i.e. push the fluid back up into the reservoir. That way you are pushing the air upwards rather than trying to pull it down. Source some silicon hose for the syringe as this is flexible and gives a good seal over the bleed nipple.
You do need to keep an eye on the reservoir to make sure it doesn't overflow - some cling film over paint is a good precaution.
When done tie the lever back over night to remove any remaining air.

One other thing to do is to put a couple of wraps of PTFE tape around the bleed nipple thread to ensure you aren't pulling in air. via the threads.
Yes. I actually filled the brake caliper with fluid and pressed the caliper piston in with a G clamp. Went in very easily. By pushing the fluid up into the master cylinder, I was hoping it would then need minimum bleeding. The system filling worked just fine, minimum to no fluid spillage. But the system did then need bleeding properly. Hence my using the syringe to suck at the bleed nipple. I have found that putting some grease on the nipple thread, then only loosening it just enough to suck fluid is a pretty good way to not draw air down via the nipple threads.
 
Yes. I actually filled the brake caliper with fluid and pressed the caliper piston in with a G clamp. Went in very easily. By pushing the fluid up into the master cylinder, I was hoping it would then need minimum bleeding. The system filling worked just fine, minimum to no fluid spillage. But the system did then need bleeding properly. Hence my using the syringe to suck at the bleed nipple. I have found that putting some grease on the nipple thread, then only loosening it just enough to suck fluid is a pretty good way to not draw air down via the nipple threads.
I’ve also used a bit of Teflon tape on the bleeder nipple threads to minimize air intrusion.
 
Back
Top