You may be getting air bubbles from the air bleeder screws (thread area where it screws into the caliper) if they are not sealed correctly. You can also pull air if the tubing on the Mityvac is not tight on the bleeder screw. Try bleeding the old fashioned way (you will need a helper) start with the caliper furthest away from the reservoir (if dual front disks) and have your helper pump the lever slowly so fluid does not splash out, then have them hold the lever while you open the bleeder, tell them to squeeze the handle until it goes to the handlebar but not to release it. Then once you close the bleeder, have them pump the lever again and repeat the process while making sure the reservoir does not get below half full. Then do the other side. If that does not get you where you want to be, remove the right caliper, and pump the lever a little making sure the pads are installed and the pistons do not come out all the way. I put a paint stirring stick in there to make sure they do not go too far. Then carefully push the pads back so you can put the caliper back on. Repeat with the other side. Make sure when pushing the pads back that the fluid does not overflow from the reservoir. DOT 5 is a little harder to get the air out of than DOT 3 or 4 for some reason.

If it is on your rear brake and you have a "S" type loop, that will hold air and you need to remove the line from the clip and remove the caliper to make the line straight, then bleed the air out of it. Good luck.

 

 

I struggled with mine for a couple weeks when I converted to 2000+ calipers. I ended up rebuilding both calipers, kit was about $30 online, then rebuilt the MC, about $20 and was still having issues. I was using a mityvac too and kept pulling bubbles no matter what. I ended up replacing the lines just to be sure, probably overkill but they were 30 years old and the last part still original on the system. Then I said F the mityvac and reverse bled the brakes by using a large syringe and pumping fluid up through the bleeder valve until it came out the MC. I did that on both sides until no bubbles were coming up out of the MC, then did 1-2 quick rounds of regular bleeding at the caliper to eliminate any air maybe trapped at the bleeder valve. At this point the pull felt pretty good, but then I took the top of the MC, taped the brake lever back around the throttle at the point where pressure was, ran it for a couple minutes, then left it taped like that over night. Came out the next day and it was an even better pull, best I had with it ever. Maybe half an inch or so pull from start to stopping the bike, its not going to feel like a new Brembo bike lever pull but its dam close.

I think those mity vacs tend to pull air in more than not so I put mine back in the box and threw it in the back of the cabinet.

 

That's good info, thanks. That reverse bleed procedure may be my next option, I'm going to give it one more shot with the mity vac tonight, going to try a different nozzle and see if that makes a difference somehow. Don't know why it would but whatever. I learned the mity vac can pull air around the loosened bleeder threads, that may be what you were finding as well, that drive me crazy for awhile until I figured that out. Anyway I solved that problem and now have a good seal judging from the amount of fluid it's pulling through. If I can't get to the "clean" fluid in a reasonable time tonight I'll try the reverse bleed process. I've never had it where I couldn't clear it up in about 1-2 mityvac resevoir's worth of bleeding, but maybe Harley brake lines hold alot more than my old racebike.

I hate these projects that should be quick and easy and instead turn into a multi hour adventure. Kind of regretting even messing with the fluid exchange, I'd rather be riding.

 

Bleeding brakes can be a bl33ding nightmare! I have several 'aids' including a Mityvac, but haven't found any of them to be the ultimate solution. I still try the old fashioned way and find that is at least as reliable as any of my alternatives. There are occasions when I have managed a fluid change and bleed in super-quick time and other occasions like your experience. There seems to be no sense or logic!

You should pray to all your gods, wait for a full moon, but above all else be persistent and patient. Try alternative methods by all means - it could be said you have persisted for too long with just one! I find it easier to bleed my brakes alone, as it can be done, the benefit being that you can coordinate the lever squeeze and nipple work more accurately IMHO. With a soft lever we can normally get pressure by squeezing several times quickly before opening the nipple. With twin brakes do the left side first.

 

For future reference I also have Speed Bleeders on several of my motorcycles, both Harley & Metric and make the process a little easier when doing the process alone. My 2000 Honda VFR800 with a mechanical linked brake system is a PITA to flush the fluid as there are about 10 steps going from front to back to front and then the portioning valve to flush the fluid. Get any air in there and there is hell to pay getting it out. Speed Bleeders made the process at least bearable. http://www.speedbleeder.com/

 

Thanks for the responses guys. I ended up abandoning the mityvac and went old school, was able to get at least a little lever pressure by gravity bleeding for a bit then I pumped the lever by hand from there old school style. That seems to have done the trick. Then I zip tied the lever to the grip over night, that seemed to have a small benefit as well. I'll probably do what Jake said as well, run the engine for a bit while I do that, I would think the vibration would help move any remaining air bubbles. But for now, pumping the lever by hand I was able to get a nice solid fluid stream out of the bleeder.

Regarding the mityvac, I have no idea what the story is there with why I was getting such an insane amount of bubbles, but who cares I guess, lesson learned. Even on my second attempt last night I probably ran another 24 oz of fluid through those brake lines and got tons of air the whole time. I know for sure air wasn't entering around the bleeder threads, I had teflon tape and silicone grease there and it held total vacuum. I tried everything, various nozzles, high and low vacuum, left side, right side, nothing worked. So I have no clue on why I was seeing all those bubbles, but after wasting all those hours chasing I'm just happy to be done. Not a big mityvac fan right now.

Don't you love it when you try to do something that's supposed to be quick and easy and it ends up being a whole project unto itself? The only reason I'm even doing this now is because I'm getting new tires this week and I figured while I have the wheels off I'd do brake pads, in which case I need to remove some fluid, in which case I may as well just do a fluid change. To get stuck on the brake bleed is crazy frustrating.

So off come the wheels tonight, hopefully smooth sailing from here. I'll check wheel bearings and swingarm play, hopefully nothing to see there. Fingers crossed cuz I want to go put some miles on my new American Elites this weekend!

 

Oh...............and I think I'm going to get a set of speed bleeders to install next time I have to mess with the brakes. Seems like a worthwhile thing to invest in, assuming the don't cause any kind of leaks or weeps. I like everything to be bone dry. Probably from my racing days, but the thought of any kind of fluids anywhere near my brakes or tires freaks me out.

 

I didn't read through every response so I don't know if this was suggested. First of all, "the old fashioned way" seems to always work best (a mighty vac or vacuum methods usually suck in air at the bleeder screw making you think it's air in the lines). I have found the best method is to push the fluid from the bleeder screw up to the master cylinder (awesome tip from HCC). Then squeeze the handle a few times and open a bleeder screw, close then pump the handle, hold and loosen the bolt to line at the master cylinder until fluid comes out. Then go back to bleeding from the bleeder screws until the pressure feels normal which should take no more than a few minutes.