Trouble bleeding front brakes!

Man has this been a nightmare! So I replaced my front M/C with a new one of ebay that was for KZ1000. Couldn't get it to stop being spongy. Then said to self "well must be wrong one" so bought one with 5/8" bore to ensure enough fluid was pressed. No change in sponginess. So then I got a ZRX M/C knowing that it had to work. Still no go. Reverse bled the brakes to get them tight. Still no glory. Bled them again and again and not getting it. How can this be? Any suggestions? Thanks, Keith

did you check the tiny fluid return hole for cloggage? that is a common issue with getting the brakes bled. did you use new crush washers? did you check for leaks?

Hi Doc, yes I seem to be ok on the return hole. No leaks and new crushed washers. I have used 3ea different M/C's on this and get the same results. Could the hoses expand that much? Is there anything that would catch the air in the lines or the calipers? I am somewhat out of ideas other than to replace all hoses with stainless, get rid of the distributiion block and rebuild the calipers. That's an expense that I have been trying to avoid but can't think of any other way to do this to get this spongyness gone. Any advice on how to proceed would be helpful. Thanks, Keith

Some folks have had success by tying the brake lever in the squeezed position over night which somehow let the air bubbles come up through the MC. Another thought is that you may want to try unbolting the splitter and calipers from the bike and turn them one way or another to let air bubbles out of any nooks or crannies they may be hiding in. Ed

If not already done, would get a new can of fresh brake fluid and do not shake it before filling the system.

Use a bulb syringe with a short length of clear hose attached that fits snugly onto the bleeder valve.

Be sure the master cylinder cover is removed.

Suck new fluid into the syringe, hold it with the tube pointing up, and carefully expel the air by squeezing it until fluid emerges from the end of the tube. And keep holding it firmly so no air can enter the tube, while attaching the tube to the bleeder valve.

With the full tube attached to the bleeder valve, open the bleeder valve, and continue gently squeezing fluid into the bleeder valve until fluid collects in the m/c reservoir.

Close the bleeder valve, and fill the reservoir, and replace the m/c cover.

Then bleed as normal.

It sometimes helps to remove the caliper and hold it so the bleed valve points straight up while bleeding.

Good Fortune!

what state are your calipers in? have you cleaned and inspected them? doubt its a hose.

Did you prime the replacement MC before you installed it?

I had the same problem on my 81 750. The lines were replaced with stainless ones, and the front lever was soooo spongy. It would pull in all the way to the grip! I bled them with a vacuum bleeder for over an hour, cracking the m/c fitting first, then working my way down. I just could not get them to firm up.

I found the solution by luck. I wondered if the m/c seals were bogus, so I was going to swap it for a known good VFR750 m/c I had. I removed the brake lever from my kaw to see if i would fit the VFRs but it didn't. So when I re-installed the lever on my Kaw I miraculously had brakes again! Apparently my plunger travel was lacking, so pulling the lever allowed the plunger to come ALL the way out and get a full stroke when the lever is pulled. I checked to make sure the brakes werent dragging and they were not. It's also possible that there was a bubble trapped in there too that removing the lever dislodged.

Long story short, try removing and reinstalling the lever

I like to unbolt the brake line from the master cylinder where it attaches to the junction block. Then remove the master cylinder cap and submerge the end of the hose in the master cylinder 3/4 full of fluid and slowly pump the master cylinder until the air bubbles stop coming out. This bleeds the air from the master cylinder. Then you can bleed the calipers after that.

I will try that this am. You never know. I appreciate everyones input it is great to come here and get some direction when I am out of good ideas. Thanks again!

In a word, no. What is this procedure? TIA, Keith

I have not gone into the calipers at this time. I'm sure a rebuild wouldn't hurt but they worked well before I replaced the M/C so, I maybe incorrectly drew the conclusion that I have created the problem. Hey, when I reply to a specific post does it come up tied in some way? I got to thinking that if I reply to one of you and don't specify my answer then it could get confusing. Just curious.