Tying lever back to remove trapped master cylinder air. Safe?

[KEITH KRAUSE]

Thought I'd make a seperate thread for my problem asking a specific question.
I'm trying to remove some trapped air in my ZX14's hydraulic clutch master cylinder. Because of about 1/2" of "free play" in my lever I believe there's air in the M/C but it won't come out with the basic bleed method or with a vacuum tool.
I'd like to try tying the lever down over-night with the reservoir cap removed of course. I've heard of people doing this with no issues. I don't know if my 14's piston assembly has a fine spring like my GS has in its M/C but if it does, do you think there's any possibility that compressing the piston inward over-night could "sag" or weaken a spring??
Thanks for any replies.

[sharpy]

Just do it you woss. Its common pratice over here and a trick of the trade. Dont need to leave the cap off as there should be a tiny vent to let it breath. A bpy racers trick is to use a cotton wrist band like the tennis players use to stretch over the mastercylinder resivour to catch any seepage IF there is any. Like i said being a clutch one you might have to lean the bike against a wall with the handle bars turned right to get everything lined up for the bubbles to escape. When it does work it works great if it doesnt work maybe ure "new" master cylinder isnt it all cracked up to be unless you 100% certain there is air in there.

[hampshirehog]

No problems at all with this trick - you'll be fine. You only have to pull the lever back a bit - weak rubber band or bit of string is fine. There's no need to ratchet it back with a zip tie on full pelt.

Sharpy beat me to it - and you can even buy those 'wrist bands' especially made (and embroidered with 'CBR' or 'GSXR' and such like) for your reservoir over here (the sports bike boys seem to like them).

[tkent02]

Do it.

[Octain]

I did it on the 850 after rebuild with no harm. Didnt help anything, but no harm.

[Steve]

I did it on the 850 after rebuild with no harm. Didnt help anything, but no harm.

You have a hydraulic clutch on your 850?

I'd like to try tying the lever down over-night with the reservoir cap removed of course.

I would recommend NOT removing the cap.

You want to keep the system sealed as much as possible to minimize the amount of moisture the brake (clutch) fluid will absorb. Leaving the cap off is just exposing all that fluid to air, where it will act like a sponge and absorb more fluid overnight than it will be exposed to in the next couple of years, until it's time to flush it again.

.

[Octain]

You have a hydraulic clutch on your 850?

Heh, duh.... For some reason I was thinking brakes.

[KEITH KRAUSE]

Heh, duh.... For some reason I was thinking brakes.

The hydraulic clutch is very similar to the brakes. Same type of bleeding methods would work on either system. Thanks for the reply.

[KEITH KRAUSE]

You have a hydraulic clutch on your 850?




I would recommend NOT removing the cap.

You want to keep the system sealed as much as possible to minimize the amount of moisture the brake (clutch) fluid will absorb. Leaving the cap off is just exposing all that fluid to air, where it will act like a sponge and absorb more fluid overnight than it will be exposed to in the next couple of years, until it's time to flush it again.

.

Leaving the reservoir cap on is fine with me.
I thought the cap had to be off to allow any trapped air to float up. That's one thing about the system I don't quite understand. The system is under pressure but the reservoir isn't. I understand what you're saying about an open reservoir attracting moisture but as for allowing air to rise up and out through the reservoir, it DOESN"T matter if the cap is on? I just thought it could escape easier. Thanks Steve.

[Steve]

I thought the cap had to be off to allow any trapped air to float up. That's one thing about the system I don't quite understand. The system is under pressure but the reservoir isn't. I understand what you're saying about an open reservoir attracting moisture but as for allowing air to rise up and out through the reservoir, it DOESN"T matter if the cap is on? I just thought it could escape easier. Thanks Steve.

The whole system is NOT pressurized until the lever is moved. The seal on the piston is just behind the little equalization hole (that pesky little hole that we keep saying MUST be cleaned out). That hole connects the fluid in the reservoir to the rest of the system. As soon as the lever is moved, the piston moves to the other side of the hole, which seals the system between the master cylinder piston and the slave pistons in the calipers. As you apply more pressure to the lever, there is a pressure increase in the lines to the caliper. As you release the lever, the pressure comes back down, reaching zero pressure as the equalization hole is uncovered. There is a little bit of air that is over the fluid in the reservoir, but it is sealed in there by the gasket on the lid. One or two bubbles coming up from the fluid are not going to change the pressure to any degree, but the gasket keeps the moisture in the air outside the reservoir from getting inside.

I don't understand the physics of why pulling the lever works, but I have done it several times and I know that it does.

.

[49er]

When the lever is pulled in, that little hole comes into play allowing any air to escape out of the pressure zone and into the fluid reservoir. But to be effective, it needs to be activated several times.

Many people have problems with trapped air, as a result of this hole becoming blocked.

[KEITH KRAUSE]

OK. Thanks for the help.
I'll get back to fixing it but I'm taking a couple weeks off to go camping with my son. I'll figure it out. I've gleaned a tip here and there from you guys and I think something will work.
If this thread is still alive, when I get back and fix it I'll let you know so maybe It'll help someone else down the road.
Thanks again!

[Hammered]

Its kinda funny cause thats how The Original Lifesaver TCB Valveworks. I guess in the sense stock, we try to remove all the sponginess and then others looks to spend money to add it back. I know I know, its a tad bit more complex than that but still.

[Suzuki_Don]

Keith did you have any success in being able to bleed your clutch master cylinder effectively?

How about an update?

[chuck hahn]

I would start by rebleeeding with a clear tube coming off the bleeder valve so youn can visually see theres no air coming out. I do it on all the brakes and I had a Nighthawk with the hydraulic clutch as well. Over bleed the sucker just to be sure its air free. The tie back of the lever has helped considerably for my brakes on a few of the GSs. I think the constant pressure actually expands the cups out for a tighter fit in the cylinder bore as well. This tighter fit makes the cups seal more positively, thus they create more pressure with less levr travel and squeezing..just my thoughts on what the method actually does. I have been 1000% sure the systems were bled before and still had spongy levers till doing the tie back method.