Need help removing trapped air in master cylinder.

[KEITH KRAUSE]

Thanks a lot for the help. I'm out the door so can't give detailed reply but I'll check in later. Again, thanks!

[KEITH KRAUSE]

Is the master cylinder at a slight angle, with the banjo a bit higher?

I know you said it would be hard to do the "bench bleed", but sometimes there is a bubble trapped in that upper corner. Can you remove the brake lever and push the piston ALL the way in with a screwdriver or dowel rod? It is usually possible to push the piston farther that way, which will get rid of that pesky bubble.

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If I have to try bleeding at the banjo, this one would be difficult. Three hands needed. My banjo is directly on the bottom of my M/C and the clip on type bars close to the tank/bodywork. Trying to use your finger/thumb on the banjo hole and pump the lever and watch/refill the tiny reservoir level wouldn't be easy. I'll try it as a last resort but will maybe try 49er's method or even buy a pump style tool. My Mityvac (model MV8020) is near useless in my opinion.
What I'd like to try first is tying the lever back over-night but I'm trying to ask others if that could damage any small/fine spring inside. Probably not as I've heard others tying back to remove trapped air and never heard them say they damaged the spring and how the M/C piston rebounds. I just want to be sure.
If that doesn't work then I'd like to take the lever off and try manually pushing the piston assembly further in than the lever does. This MIGHT squeeze the trapped air out. But again, I need to ask how safe that method is. I'm not going to cram the piston in real hard, just poke it in until I feel obvious resistance that tells me to stop. I just don't want to push it in and find out I screwed something up by doing that. I don't need to add problems.

[Suzuki_Don]

Keith, with this being a clutch lever, does the lever come all the way into the handlebar the same as a cable type lever does. And if so then there is a difference here in cable tying the lever to the handlebar.

When you cable tie the brake lever to the handlebar, the lever only comes in about halfway to the handlebar until the pressure builds up in the system and the lever reaches that position. But if the clutch lever comes all the way to the handlebar then I am unsure if this will create enough pressure to remove the bubble in the system.

I don't know whether this will cause a problem or not.

[KEITH KRAUSE]

Keith, with this being a clutch lever, does the lever come all the way into the handlebar the same as a cable type lever does. And if so then there is a difference here in cable tying the lever to the handlebar.

When you cable tie the brake lever to the handlebar, the lever only comes in about halfway to the handlebar until the pressure builds up in the system and the lever reaches that position. But if the clutch lever comes all the way to the handlebar then I am unsure if this will create enough pressure to remove the bubble in the system.

I don't know whether this will cause a problem or not.

Good thought Don. I'm so thinking the clutch and braking systems are alike but that IS one difference. The hydraulic clutch doesn't continue to build that pressure the more you squeeze the lever like the brake. It does pump up but you can easily pull it to the grip which is how it's used in operation. Can't do that with a properly operating brake.
I'll probably still try it since others say there's no danger of damaging something in the piston assembly. But now I have less faith it will work.
I appreciate the help.

[KEITH KRAUSE]

Yeah the tieing the lever back works great in desperate times. Just make sure everything is set so air will flow up and out. Might mean leaning the bike againt a wall with the handle bars turned to the right overnite.

Someone at a ZX forum mentioned the same thing about leaning the bike to the right. I haven't tried it but this bike seems like it would be difficult to lean. The bars don't stick out much beyond the bodywork and the mirrors stick way out. The mirrors don't like to be tampered with I've heard. They lose their ability to stay tight but still be adjustable.
I appreciate the help. I'll see about leaning it. If I can do it safely I'll give it a try.

[TheCafeKid]

Someone at a ZX forum mentioned the same thing about leaning the bike to the right. I haven't tried it but this bike seems like it would be difficult to lean. The bars don't stick out much beyond the bodywork and the mirrors stick way out. The mirrors don't like to be tampered with I've heard. They lose their ability to stay tight but still be adjustable.
I appreciate the help. I'll see about leaning it. If I can do it safely I'll give it a try.

Keith is there a slave cylinder? An air bubble in the slave will give the same feel as on in the master. Not the same Kaw I know but as I said my ZRX has a hydraulic clutch and it has a hard line with banjos running from a spliter (fed by the MC) to the slave cylinder down on the motor (in my case easy to get to as there is no bodywork, you may have to remove yours to get to your slave cyl).
I'm with you on not being certain tying the lever back will do any good simply because the lever will go to the bar and may not necessarily be at full stroke in the bore.
When I've had problems with brake MCs in this situation I've removed the MC and took it to the bench.. Already suggested I think but this may be the only way to get it out. I set a dowel or a dull drift in a vice, poured fluid directly down the MC bore via the banjo fitting outlet, (with the resivour already filled) and then used the dowel to push the piston to full stroke while keeping my thumb over the banjo hole. It's seemed to be fairly effective every time. Most times a heck of alot moreso than pumping your brains out with a silly mitey vac.,..

[Macmatic]

Not sure how this is set up but what about bleeding the slave like a temperamental caliper? I'm thinking of cases where you have to push the piston back into the bore with clamps to fully bleed the caliper, maybe you could pull the slave and use three hands and both feet to push the clutch rod actuator back into the slave while you bleed it.

/\/\ac

Is is bad that this was my waking thought today?

[KEITH KRAUSE]

Thanks for the help. I'm working on it. Can't believe what a pain it is.
Anyway, I'm taking a couple weeks off to take my youngest son on a camping trip through Colorado/New Mexico.
When I get back I hope to fix it. I do appreciate all the help!

[chuck hahn]

I have read this and its my opinion the only way to get air out is to bleed it out the bleeder nipples. The purpose of tying back the levers really is that with the hydraulic pressure applied and maintained for an extended period, this causes the rubber cups to stretch and reatain that memory so as to effect a tighter and more effective seal against the cylinder bore. This tighter seal in turn makes the lever much harder and sensitive because the cups are sealling positively and not allowing fluid bypass to occur. If air will " leak back" and come out into the resivoir cup then that should tell you right away that the cups arent sealing and doing their jobs in the first place. Thank you.