Clutch Master Cylinder questions KrZy8

[dcarver]

2006 with almost 250k miles. 

Clutch goes soft overnight. No visible leakage at slave or mc fittings or along hose.

Possible it's leaking back through the piston seals?

Multiple lever actuation restores pressure, but not completely. 

Bleeding restores 100%.

Once done, it holds pressure as long as bike is ridden.

Academic question really, I bought a 4,300 mile used MC from eBay.

Just wondering if piston seal leak by is a good guess.

 

[FJRay]

It's old age Don. Lots of things go soft overnight.  unk: :****:

 

[Road_Runner]

Mine is doing exactly the same thing.  2008 w/only 24K, but was sitting a lot before I bought it a few months ago.  I already changed the fluid (which was hella nasty) and have bled it twice with same results... solid lever for a while, then have to pump it up for the day.  I figure leaking at piston seal also, just not sure which end.  Going to take it apart this weekend, and inspect before ordering a master cyl rebuild kit or a new/used slave cylinder. 

I will post when I find something out.

Are you done with the 2006?

 

[Road_Runner]

Actually I found some more information:

I see in another thread that you first replaced the slave cyl to an earlier one with more throw.  You then discovered the air leak issue in this thread?

I see that you also replaced the master:





That fix it?

 

[dcarver]

Actually I found some more information:

I see in another thread that you first replaced the slave cyl to an earlier one with more throw.  You then discovered the air leak issue in this thread?

I see that you also replaced the master:





That fix it?

I replaced the Gen 2 MC with Gen 1 years and many many miles ago. Then the softness started. My first thought was the slave cylinder, so put the OEM unit back on. Which didn't fix the problem. Given no visible leaks the logical thought was the MC leaking by. Replacing the MC fixed the issue for me. Hope this helps!

 

[Road_Runner]

I replaced the Gen 2 MC with Gen 1 years and many many miles ago. Then the softness started. My first thought was the slave cylinder, so put the OEM unit back on. Which didn't fix the problem. Given no visible leaks the logical thought was the MC leaking by. Replacing the MC fixed the issue for me. Hope this helps!

Thanks for responding.   I have a clutch master rebuild kit OTW - I chose this path to start because it is far cheaper than a new or even a used slave.  I would have just torn it apart and see if it just needed cleaning, but I need my wheels!

 

[RossKean]

Thanks for responding.   I have a clutch master rebuild kit OTW - I chose this path to start because it is far cheaper than a new or even a used slave.  I would have just torn it apart and see if it just needed cleaning, but I need my wheels!

Out of curiosity, where did you get the rebuild kit?  Yamaha or something aftermarket.  Cost?  Not much to it and if it wasn't stupid expensive, I would probably go for new seals rather than just cleaning, especially on a 12 year old bike.  Mine is a 2011 but no issues so far.  Same with the previous high mileage '07.

 

[dcarver]

Out of curiosity, where did you get the rebuild kit?  Yamaha or something aftermarket.  Cost?  Not much to it and if it wasn't stupid expensive, I would probably go for new seals rather than just cleaning, especially on a 12 year old bike.  Mine is a 2011 but no issues so far.  Same with the previous high mileage '07.

Yamaha. https://www.partzilla.com/product/yamaha/5JW-W0041-01-00?ref=bc28119f23c1ee033fa50e11197ccc9d5e85fb95

 

[Road_Runner]

Yes I ordered a rebuild kit:

https://www.ebay.com/itm/Clutch-Master-Cylinder-Rebuild-Repair-Kit-Yamaha-FJR1300-VMX1700-VMax-32-4195/312399799197?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

It was only $18 w/free shipping.  Probably would have went with a Yamaha kit for a few bucks more if i knew they existed.

For only $18 I figured it would be better to go ahead and replace the seals.  Any idea of the lifespan of the brake lines?  Thinking about ordering some Galfer brake lines.

 

[RossKean]

Never heard of hoses wearing out or deteriorating.  Wouldn't bother unless you have a leak or a bulge.

 

[Road_Runner]

Rebuild kit for the clutch master cylinder has been installed.  I had already changed out the fluid a while back, and it was clean in the master reservoir and was coming out clean when I was bleeding, but the master was very nasty with some sludge and grime in there.  Due to brake fluid being hygroscopic, and due to it never have been changed, there was also corrosion on the steel bolt that secures the brake line.  The old piston and seals did not seem to be in bad shape though.

I will know shortly if that fixed my slow air leak.

For anyone finding this thread who is planning on performing a clutch cylinder rebuild in the future:  After you get the clutch master off, the first thing will see in the cylinder bore is a rubber dust sleeve.  It is just jammed in there and is not held by a clip or anything.  Simply pry it out with a pick to get to the circlip. 

 

[YummYam]

  After you get the clutch master off, the first thing will see in the cylinder bore is a rubber dust sleeve.  It is just jammed in there and is not held by a clip or anything.  Simply pry it out with a pick to get to the circlip. 

Good tip. Wish I knew the f brake master has the same deal when servicing mine last week. 

 

[Road_Runner]

My issue is resolved - rebuilding the clutch master cylinder did it.