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Me, Judy and the pup were out for a ride today on some new roads. I missed a turn and ended up on a dead end road and had to turn around on a grade. We were chatting and laughing and apparently not paying attention and when I was slowing to a stop while turning left, mostly straight to get ready to back up and finish the turn. The roadway to my left was steeper than I had thought and that's the way we kept going. Everyone for themselves at that point. Judy's version is more colorful. Everyone is fine.

The real purpose of this post is this. After we remounted and pulled away, the clutch engagement was way different. Much closer to the handlebar. Checked the lever position adjuster still at 1 as usual. Looks like the piston adjuster screw hasn't moved, still loctited in position. All I can figure is that the orifice in the master cylinder allowed air in during the spill. Anyone else experience this before. Or any suggestions on what else could be wrong? Time for a fluid change anyway. Just curious what others think.

Thanks
 

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bowlesj said:
The real purpose of this post is this. After we remounted and pulled away, the clutch engagement was way different. Much closer to the handlebar. Checked the lever position adjuster still at 1 as usual. Looks like the piston adjuster screw hasn't moved, still loctited in position. All I can figure is that the orifice in the master cylinder allowed air in during the spill. Anyone else experience this before. Or any suggestions on what else could be wrong? Time for a fluid change anyway. Just curious what others think.

Thanks
Air is likely, but before bleeding (which requires pushing the air all the way down the line to the slave cylinder, then out the remote bleeder), I'd turn the bar full right (clutch reservoir high), tie the lever to the grip, and let the bike sit overnight -- the hope is to let the air rise of its own accord.
 

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Discussion Starter #3
mneblett said:
Air is likely, but before bleeding (which requires pushing the air all the way down the line to the slave cylinder, then out the remote bleeder), I'd turn the bar full right (clutch reservoir high), tie the lever to the grip, and let the bike sit overnight -- the hope is to let the air rise of its own accord.
Thanks for the reply Mark. I was hoping you or David S. would have a thought on this.

Definitely worth trying your technique first. The trapped air should be near the master cylinder. Let's hope this is all that is wrong.

Thanks again.
 

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mneblett said:
Air is likely, but before bleeding (which requires pushing the air all the way down the line to the slave cylinder, then out the remote bleeder), I'd turn the bar full right (clutch reservoir high), tie the lever to the grip, and let the bike sit overnight -- the hope is to let the air rise of its own accord.
Mark, wouldn't tying the lever back block off the hole to the reservoir?

I would do as you say, but leave the lever out so the air has a path back into the reservoir.

I had the same thing happen to my front brakes once (nasty surprise at the first stop), and just let it sit overnight, next morning the brakes were fine.
 

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Discussion Starter #5
Well guys thanks a lot. I read what David said and it made a lot of sense. So not knowing if there was anything different on this master cylinder piston than others I figured I would give both theories a try. The lever had been clamped all day while I was at work rebuilding another type of German gearbox. About 10 hours. Then when I got home I undid the tie to let it sit overnight, no need.

The clutch lever pressure was back to normal and engagement correct.
So it did work with the lever pulled and tied down.

Just so others know - with this spongy clutch the start switch at the clutch was open before the clutch would disengage, Therefore if the clutch wasn't pulled all the way to the bar the bike would try to start while in gear. This is how I checked it to make sure I wasn't imagining anything.

Thanks again for your time and help Mark and David,
 

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dshealey said:
Mark, wouldn't tying the lever back block off the hole to the reservoir?

I would do as you say, but leave the lever out so the air has a path back into the reservoir.

I had the same thing happen to my front brakes once (nasty surprise at the first stop), and just let it sit overnight, next morning the brakes were fine.
In fact take the top cap off the reservoir . This will help the air escape if that is the reason for the lever difference
 

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dshealey said:
Mark, wouldn't tying the lever back block off the hole to the reservoir?

I would do as you say, but leave the lever out so the air has a path back into the reservoir.

I had the same thing happen to my front brakes once (nasty surprise at the first stop), and just let it sit overnight, next morning the brakes were fine.
That's exactly what I thought when I first heard of this, but for reasons I can't explain easily, it works.

The only thing I can guess is that the air rises to just behind the piston, and then when the lever is released, it is near the piston where it is easily sucked back out into the reservoir -- I've watched fluid shoot straight up into the air at least a foot if the lever is released suddenly with the reservoir uncapped, so the suction there is pretty strong. As I said, somewhat counterintuitive, but I've decided not to fight this one with logic anymore. :)
 

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Be Careful Leaving Cap Off Overnight

Someone suggested (in an earlier post) to leave the cap off the brake fluid reservoir overnight. I would not recommend this, as brake fluid is notorious for absorbing water from the atmosphere. If you read most owners/service manuals you will find warning; "Use only DOT ___ Brake fluid from a SEALED container." This is directly related to this issue. I would never leave my system open overnight. Just my 2 cents.
 

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Discussion Starter #9
Yea Jack, that's what I was thinking too. I thought about leaving the cap off or loose to expedite things but decided against it due to 80% humidity and rain in the forecast. I'm getting ready to do a 24K/annual and the moisture may have been a moot point, but no need to purposefully introduce water. As it was, the clutch is good to go again using Mark's technique exactly.

Have a good 'un
 

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bowlesj said:
--------------------------------
The clutch lever pressure was back to normal and engagement correct.
So it did work with the lever pulled and tied down.---------------
Glad it worked. Thinking about it, there needs only be a small amount of air in the line to cause a big problem, and that air will work it's way back up to the master cylinder. It cannot get to the reservoir with the piston in, but when you release the lever the flow of fluid back into the cylinder will take the small amount of air with it.

Still, I think it is better to leave the lever out, with the bar turned full right. That way the air will work it's way right into the reservoir.

Also, with the problem of slave cylinder leakage causing clutch problems, I would not want to keep pressure on the slave cylinder for long periods of time.
 

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murray said:
In fact take the top cap off the reservoir . This will help the air escape if that is the reason for the lever difference
I would not do that. The fluid in the reservoir is at atmospheric pressure, but not exposed to the ambient air due to the little rubber diaphragm in it. The top of the diaphragm is vented via a small opening in the cover seal area, but the bottom is sealed to the reservoir, trapping only a small amount of air over the fluid. You do not want to expose the fluid to ambient air any longer than absolutely necessary due to moisture absorption.
 
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