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Discussion Starter · #62 ·
Just one more question the answer to which will likely confuse me more.:surprise:

Does the problem go away if you let the scooter cool or do you still have to bleed at the slave cylinder?
No the air lock stays, I've left for a week (didn't have the right tools) before bleeding the slave cylinder and it was the same just a quick loosen a partial squeeze on the lever until fluid is seen, tighten bleed nipple, all is back to normal operation.
 

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Just Winging It
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The more I think about it here's what I think is happening.

The rubber in the slave and/or the master is failing.

And

Perhaps the heat is heating moisture in the dot 4 causing the clutch to fail.

Wet boil point 311f dry 446f

Unsealed dot 4 sitting on a shelf collects moisture.

Brake fluids are hygroscopic (water absorbing).

I doubt the slave is getting to 311f

New dry dot 4 fluid would bump the boiling point up over a hundred degs.

Possibly dot 5 was used at some point.
 

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As expected I'm more confused.
If the brake fluid was boiling from the heat I would expect it to condense when cooled.:?
OK...I Googled it. Heck of a hard time figuring out what to search for. Anyway...this is for water. It may or may not apply here. When water is boiled or evaporates it becomes a vapor. . When it condenses there is non-condensable gases present. (air) Don't ask me how what or why. The article was too long for me to read the whole thing. You can if you like. :wink2: Here you go:

http://www.plantengineering.com/sin...-system/79fa6a7fd7616f5cce50120f709d8d2c.html

noncondensable gas[¦nän·kən′den·sə·bəl ′gas]
(materials)
A gas from chemical or petroleum products that is not easily condensed by cooling; consists mostly of nitrogen, light hydrocarbons, carbon dioxide, or other gaseous materials.
 

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Just Winging It
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And the boiling point of dot 4 lowers as the moisture increases.

Moisture also known as water is H2o hydrogen and oxygen or air.


 
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1987 GL1200 Interstate
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Interestingly, or depressingly, if you will, my clutch is starting to display these symptoms, again.

I just rebuilt both master and slave, but admittedly the master felt sticky, like it was trying to hang up, from the get-go. I suspect I overlooked oiling one of the pieces when assembling.

Any news Johno?
.
 

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Interestingly, or depressingly, if you will, my clutch is starting to display these symptoms, again.

I just rebuilt both master and slave, but admittedly the master felt sticky, like it was trying to hang up, from the get-go. I suspect I overlooked oiling one of the pieces when assembling.

Any news Johno?


.
Another and maybe more likely possibility is that, with the miles on the bike, the bore of the master has worn. It is larger and allowing the piston to **** in the bore. Another possibility along the same lines is the piston is so badly worn that the piston to cylinder clearance is so great it cocks in the bore. Or even a combination of both. Did the piston look scored at all? Piston to cylinder clearance in a master cylinder can be as little as .001 inches. it is difficult for the average backyard mechanic to measure this distance. If you lube the piston and devise a way to pull the piston back you can do a backyard check. With the bore and piston covered with brake fluid. Piston all the way in, cover the outlet port with one finger. Now pull the piston out quickly. It should make a pop noise. If it just comes out easily the piston to bore clearance is probably too lose. (worn) I wonder how many times a guy uses the clutch in 285,000 miles? >:)
 

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1987 GL1200 Interstate
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That's actually the second master, Mike. After having the first bled and rebuilt a few times, I found a newly arrived and well cared for, but crashed, '86A in the local graveyard. Snagged the master and placed it on Bike with no more than a quick bleed. That was at 68,000 miles and it didn't give me a speck of trouble until just recently.

It may be worn out but when I put the kit in last January (278K miles) it felt like something didn't get lubed and I kind of figured I'd be doing it again fairly soon. I'll bleed the system just to make sure I'm not dealing with a phantom bubble, though.

Anyway, I don't mean to hijack this thread, but would like to point out my symptoms are very similar to Johno's.
 

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Discussion Starter · #71 ·
Any news Johno?
.
There may be a little delay before I get any further, I work away from home during the week. Due to the heavy summer traffic, rode my NT700Va this week and will do again next week, then I'm out of the UK for 3 weeks so may not be able to provide any further input on subject until August, although I will be out and about on the GL over the weekends so may find something new now I know roughly what I am looking for.

Sorry for leaving you all hanging......:wink2:
 

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Please bookmark this thread for yourself so you can find it when you do get time.
 

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Discussion Starter · #73 ·
sorry for the continued delay for an update.
I took the Combi out a few times in summer with passengers etc, but as it was only short distance slower runs, the issue didn't re-appear.
I was then supposed to be working abroad until mid December, but had a trip fall in October causing a Distal fracture of my right femur. having flown back to the UK I was sent in for an emergency operation as my femur had split down the centre:surprise:. I now have a metal plate and screws holding it all together.
It will be a while until I can ride again, but at least with the sidecar I won't have to support the weight of the bike on my healing leg, So around Jan/Feb, when I can and if the winter permits, the GL will be my first priority!:praying2:
 
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