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

KEITH KRAUSE

KEITH KRAUSE

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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.
 
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.
 
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).
 
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I did it on the 850 after rebuild with no harm. Didnt help anything, but no harm.
 
Octain said:
I did it on the 850 after rebuild with no harm. Didnt help anything, but no harm.
Click to expand...
You have a hydraulic clutch on your 850? :-k



KEITH KRAUSE said:
I'd like to try tying the lever down over-night with the reservoir cap removed of course.
Click to expand...
I would recommend NOT removing the cap.
noway.gif


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.

.
 
Steve said:
You have a hydraulic clutch on your 850? :-k




I would recommend NOT removing the cap.
noway.gif


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.

.
Click to expand...
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.
 
KEITH KRAUSE said:
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.
Click to expand...
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. :D

.
 
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.
 
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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!:)
 
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. :confused:
 
Keith did you have any success in being able to bleed your clutch master cylinder effectively?

How about an update?
 
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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.
 
Suzuki_Don said:
Keith did you have any success in being able to bleed your clutch master cylinder effectively?

How about an update?
Click to expand...
No. Gave up trying.
I'm fairly certain there's a little air in there but can't find a method to get it out.
The one reason I think there's air in there is when I was bleeding the slave cylinder down below with my Mityvac, I allowed the reservoir to get too low (it's really small). Before that happened I always had about 1/4" of lever "play" at the most. After the reservoir went low I had about 1/2" or somewhere in between. Not much difference but if it was your bike you'd KNOW something's changed.
I could see the reservoir bottom was basically dry but it's still hard to believe the hose going to the M/C was also dry and air could get stuck somewhere. With the new vacuum tool I bled the M/C at the lever just fine and I thought I had a good timing routine going on when I switched to the slave but I was too slow and let the fluid get low.
All I know is the extra play happened at the same moment so I guess there's still air in it.
The clutch works fine but I wish I could find a method. I asked at a few ZX forums but no luck when trying what they said. I've tried so many ways I got tired of it. I'll probably never use that Mityvac again. Not the tools fault but we don't get along. I tried vacuum. I tried pumping fluid UP through the system. I tried the basic method until I got sick of it. One member at a ZX14 site said other members had trouble bleeding too but if you leaned the bike to the right it helped the air pop out. So instead of leaning the bike over I actually took off the entire bar/lever/MC as a unit and had my son hold it at various angles while I bled again. No air would come out. Makes no sense because the factory places the bleed valve at the top of the M/C and any trapped air should find its way out. I don't know how any air could stay in there after all my different attempts but what can I do? One time while my son was holding the unit I was a tad slow closing the valve and I knew I sucked in just a bubble or two. In less than a minute we saw that air pop out while using the basic method. So why the same method won't work on any other suspected air in there is beyond me.
I always try to pass on any info I have that might help others so if I find the fix I'll let others know. Thanks for the interest.:)
 
piston stuck?

piston stuck?

wondering if the piston in the master cylinder didn't return all the way? john
 
Tie back lever approach and Tap,Tap,Tap w/plastic screwdriver handle or other favorite item at MC banjo bolt,follow line,tap,tap down entire length of hose,tap,tap,slave cyl.Tap going up now ,Slave cyl every inch of hose to MC banjo bolt.Gentle continue/repetitive tapping,operate lever also during tapping.Play favorite drum solo in head on /at clutch/line and componets up and down,back and forth. 2008 B1250S ABS,brake bleed job ,gave me fits,this actually did make that diff I.was desireing.Just maybe to consider, if have not done yet. PS.took multiple tries before process worked(no air in line/good feel).Other time problem "resolved" itself by just riding,I think bike/engine/road/lever MC usage vibed out stubborn remaining trapped air. Am thinking to try(or maybe some member,do it) use vibrating device like...? ,electric razor,hair clipper in contact w/hydraulic system lines/operating cylinders.
 
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