Master cylinder warning signs?

[JPaganel]

So, a couple of days ago I went to work.

The bike was hard to get in gear. Also, occasionally it behaved like clutch wasn't disengaging, stalling and pulling with the lever pulled in.

The next day, it was absolutely fine.

I don't see any external leaks, and the fluid is clear and at proper level. Am I correct in thinking that the master cylinder seals might be giving out?

[Mike 86 in San Dimas]

Does the pull on the lever feel "normal". Might try bleeding. As you probably know these often leak at the clutch slave cylinder. Evident by fluid trailing down from it. If not done already, look closely down there.

[JPaganel]

Feels normal now.

This really lasted one day.

There are no traces of leaks at the slave cylinder. I would also think that if there was a leak, I'd see fluid level dropping.

[Bill_Rockoff]

When my bike was doing that, it turned out to be a slow leak in the slave seal. Heat would embrittle it (because I sat in Atlanta traffic a lot) and it would let a little fluid out / air in, and it would get a small air bubble in the bottom. This would make the clutch fail to disengage completely when I pulled the lever in.

Wiggling the clutch hose by the slave cylinder would help the bubble rise to the top, so it would ride normally for a while. The problem would crop up again, usually when the engine got hot.

Of course, more air in the master reservoir means less fluid in the system, and after half a summer mine would be visibly low on fluid. And of course the fluid is going somewhere. This was evident when I pulled the slave cylinder to replace the seal, and the bottom / hidden part of the housing was covered with all this grimy crud made up of chain lube and road debris and the couple of ounces of hydraulic fluid that had leaked out.

For a while, when I was riding 5,000 to 10,000 miles a year and some of it was a commute in Atlanta rush-hour, I was doing the slave seal every couple of years.

If the fluid is old and has accumulated a lot of water, you may need an entire slave cylinder. But if not, you can fix this long-term for a couple bucks worth of brake cleaner, a couple bucks worth of brake fluid, and a slave seal kit from RPM (like $20.) You'll have to pull the shift linkage and the sprocket cover to get the slave cylinder off, IIRC, so it's a 10mm box wrench for the linkage bolt and IIRC an 8mm socket to pull the covers off (don't mix up the bolts, they're different lengths.) I think it will take you about an hour, hands-clean to hands-clean. For me the hard part was always "the master cylinder cap screws" because I never knew it was a JIS screw and not a Phillips head.

DO NOT start the engine with the slave cylinder removed, or oil pressure will shoot the clutch pushrod out the left side of the engine. I think there is a ball bearing at the clutch end of it that will also get fired out of the engine and lost, or will wind up inside the engine someplace that would be a really bad place for a random ball bearing. Also, watch for dripping fluid from the master onto the paint.

Good luck.

[JPaganel]

Bill, that's great info.

So, I had a bubble, and it filtered out, but it's not a big enough leak to show up.


I already have a slave kit - bought it for the previous FJ, but never got a chance to put it in. Fluid is shiny new, just got it in end of last summer.

Not worried about paint - chin scoop is off, I've been gluing it.

[a.graham52]

How's your engine oil? Running motorcycle specific oil correct? Also is it due for a change. Oil condition can directly effect clutch performance

[ct7088]

I replaced my slave cylinder two years ago with a new RPM slave cylinder. I rebuilt the master cylinder. This is after the bike sat for twenty years and sometimes in the morning the bike pulls when I start it in gear. I haven't identified anything different from the previous days ride that would cause the dragging discs. Once started there is no difference from any other day. The clutch disengages completely in less than one and a half inch of lever travel and is consistent. The master cylinder is original.  I did change to Mobile One 4T because shifting was so much smother than with the Castrol 4T. This is a clunky transmission and it is easy to understand why the shift arms get bent on the older bikes. The original slave cylinder had a deep ring of corrosion in the area where the seal rides and the RPM slave cylinder at $87.23 made sense to me.

Chris

[Mark Olson]

A common occurrence that happens when someone pulls in your clutch lever while on the side stand and the master is not filled to the top.
allows air into the line and will magically fix itself the next day after the bike sits. 

[ribbert]

A common occurrence that happens when someone pulls in your clutch lever while on the side stand and the master is not filled to the top.
allows air into the line and will magically fix itself the next day after the bike sits. 

Even worse if turned on left lock as well and I've found they self bleed faster in use, a couple of blocks will see it right again.

Noel