Front Brake Bleeding Trouble on Sportster build

[cncannone]

I pulled everything off a 1997 1200 and threw it back into a rigid frame. I'm having issues bleeding the front brakes now though.

I hooked the brake line back up to the master cylinder, bolted the caliper back on, attached the brake line to the caliper and tried to manually bleed the brakes. Nothing happened.

Undid the banjo bolt from the caliper, pulled the brake lever and fluid is definitely traveling from the m/c to the end of the brake line.

Picked up a mityvac and it's been pulling a ton of air and a little fluid but it never gets to the point that it's only pulling fluid. Went through 2 m/c full of Dot 5 and I'm still getting mostly air.

Filled the caliper with Dot 5 through the banjo bolt hole and the mity vac sucked that fluid out through the bleeder but then went right back to mostly air.

Tried plugging the opening in the mc with my thumb and pumping the lever, took the caliper off and held it above the mc, kept using the mityvac, tried manual bleeding and no luck.

Just zip tied the lever to the throttle grip to see if I can get the air to come out the top and will check it tomorrow.

In the meantime, any ideas on why I'm getting so much air but it never starts sucking out just fluid?

I have the inspection with State Patrol to title my build on Monday. Hoping I can figure it out before then. This is all that's holding me up.

[joel73]

What I do when they don't want to bleed is hook evrey thing up tight but leave the top of the hand control off fill it up and pump it maybe 30 times as fast as I can. now with the lever out tap the caliper and brake lines from the bottom to top with a screw driver handle. Then watch the fluid and pull in the handle.You will see lots of air bubbles. let the handle out and start tapping again, repeat untill there is no more bubbles. Then bleed the brakes like you would normally. this has alway's worked for me.

[elmiguel13]

If your only getting air it sounds like there is a leak somewhere. Maybe your brake line is bad, even with my cheapo harbor freight pump I can usually pull through about one MC full of fluid, pump the lever a few times and feel pressure. Couple of cracks on the bleeder valve and i'm fully bled. Id check the brake line.

[tyszko]

rebuild the master cylinder had one do that found leaking around the o ring in cylinder.

[Guest]

I had the same problem with a sporty I did two years ago. What worked for me was I hung the caliper from a coat hanger above the brake lever, then used the standard bleeding ritual, squeeze lever,open bleeder,close bleeder, release lever. Resistance came right up on the lever, worked really well. It was a pain to do by myself but it was the only way it would work for me. Bubbles want to go up,not down.

[nateridesbikes]

Mine is doing the exact same thing right now.

[TheYetti]

I had that issue, found that air was leaking around the bleed screw. Put some thread tape on it and finally got it bled.

[Braaap]

fuck the bubbles and fuck the mightyvac - use 1/4" tubing and an oral or cooking syringe to reverse fill thru the bleeder valve with the positive pressure from the syringe. watch the res fill up, cap it and be done. if it still has any issues rebuild the mc, and/or try to bleed it traditionally after the positive pressure syringe fill

+1 on the thread tape for the bleeder.

[Guest]

That sounds like it would work

[cncannone]

Rebuilt the m/c, everything is good now. One of those situations where the logical answer is the right answer and you ignore it because the logical answer can never be right.

Thanks for the help

[13clicks]

This may help others... Sometimes the calipers have brake fluid jelly if the bike is older than 10yrs and never serviced. This is only if you are lazy and don't want to spend $ on a rebuild kit.

1 Take off the calipers from the forks or rear end.

2 pump the brakes until the pistons pop out as far as they can (make sure your brake fluid is never low enough to suck air in the master... Keep an eye on the fluid level as you pump the pistons out because you are going to use a lot to pop out those pistons)

3 take a large standard screwdriver or small pry-bar to widen the disc pads out as far as they go again watch for the fluid to spurt out so go slow and have something to catch the overflow. (Keep the fluid off any painted areas because this shit will eat paint like it's going out of style. Gloves are nice if you are a hipsterhomo)

4 Repeat steps 2-3 about 4 times to get the system cleaned out.

This is basically exercising the caliper and cleaning out the gunk on the cheap.

[cncannone]

This may help others... Sometimes the calipers have brake fluid jelly if the bike is older than 10yrs and never serviced. This is only if you are lazy and don't want to spend $ on a rebuild kit.

1 Take off the calipers from the forks or rear end.

2 pump the brakes until the pistons pop out as far as they can (make sure your brake fluid is never low enough to suck air in the master... Keep an eye on the fluid level as you pump the pistons out because you are going to use a lot to pop out those pistons)

3 take a large standard screwdriver or small pry-bar to widen the disc pads out as far as they go again watch for the fluid to spurt out so go slow and have something to catch the overflow. (Keep the fluid off any painted areas because this shit will eat paint like it's going out of style. Gloves are nice if you are a hipsterhomo)

4 Repeat steps 2-3 about 4 times to get the system cleaned out.

This is basically exercising the caliper and cleaning out the gunk on the cheap.

I had tried this too but it didn't work for me. My mc was just that effed I guess

[Cruza]

fuck the bubbles and fuck the mightyvac - use 1/4" tubing and an oral or cooking syringe to reverse fill thru the bleeder valve with the positive pressure from the syringe. watch the res fill up, cap it and be done. if it still has any issues rebuild the mc, and/or try to bleed it traditionally after the positive pressure syringe fill

+1 on the thread tape for the bleeder.

+2 with this answer (air rises)... when I'm totally re doing the brake fluid I flush the brake system with metho, let it air dry then refill with b/fluid.
The metho will drain any brown sludge out, works for me ... even on cars.

[taurus4life]

+1 on the syringe. done it with my sporty. just go to any medical supply store and ask for a irrigation syringe, then get some hose and connect it to the bleeder valve and push brake fluid through. make sure there is something covering brake fluid reservoir because it will shoot all over the place. but it works the best at getting any air out of the lines.

[lowlife32]

I always use the syringe method, its just so much fn easier and Ive never had it fail me. I usually get my syringes at any livestock supply store. maybe like .5o cents each.