[83Sabrevf750]

1983 Honda Sabre Vf750s. The bike runs great now except for the clutch.
Hydraulic, multi-plate clutch
flushed the line and bled it without change
ordered a slave cylinder rebuild kit but haven't received it yet.

Has anyone heard of this: ill start up the bike just fine and it idles perfectly but when I shift into first, if I don't take off right away, the clutch slowly disengages like I'm letting out the handle when I'm not. the bike either stalls out or jerks around until I take off. same think when I come to a stop.

I don't know what to do!! is it a fluid leak or a plate issue?

 

[Eye_m_no_angel]

It sounds like something is causing you to lose pressure in the system. If it's a leak you should be able to find that easy enough. (Look for the fluid dripping somewhere.) It could also be a master cylinder seal or o-ring failing, which would allow pressure to bleed back into the reservoir.

 

[83Sabrevf750]

ok, I don't have any fluid leak near the master cylinder but there was something by the slave cylinder banjo bolt I could check out. Could a slave cylinder seal allow a leak into the reservoir or would it have to be the master?
Thanks very much for your help

 

[WintrSol]

The master cylinder is at the bottom of the reservoir, and the slave is at the other end of the line. If the slave is leaking, it has to be to the outside, so you will see fluid wetting something around it; only the master can let fluid back into the reservoir.

 

[Critter]

Air in the line? Try bleeding it again.

 

[83Sabrevf750]

ok so ill do the rebuild to the slave and make sure to bleed it good after. No fluid leaking from the reservoir but what seals should I be checking to see if it is leaking back into the reservoir?

 

[SemiFast]

It sounds like the master cylinder seals are not holding pressure and fluid is leaking around them.

The seals in the master cyl are on a piston inside the bore. You can count on them needing replacement. (They're 'leaking down' after all).
Also, check for pitting in the bore. Other than that just clean up the internal parts. Make sure the holes in the bottom of the reservoir are clear.

I would recommend overhauling the master cyl BEFORE you do the second (slave) cyl.
Any trash in the master cyl will make its way into the second cyl when you bleed the system.

 

[83Sabrevf750]

Whats the bore?

 

[SemiFast]

I call it a bore. There may be a proper or better name for it, don't know. The inside of it is like that of a round tube.

The bore is inside the roundish area below the reservoir. The lever pushes a rod up into that bore when the lever is pulled in.
That rod pushes the piston/seal assembly (inside the bore) creating and holding pressure while the lever is pulled in.
Worn seals, trash or pits in the bore can make it 'bleed down' causing a loss of pressure while holding the lever in.

 

[WintrSol]

I call it a bore. There may be a proper or better name for it, don't know. The inside of it is like that of a round tube.

That is the correct term. Whenever you have a piston moving in a hole, that hole is called a bore; probably because you use a boring tool to create it. Same for engines, firearms, etc.

 

[83Sabrevf750]

ok cool, thank you all very much. as soon as I get back home I will check all these things and see what happens

 

[83Sabrevf750]

The slave was rebuilt without change. still losing pressure after holding the clutch. I think SemiFast was right about the seals on the master, they are shot. so that's the next to go but if its not that I don't know. We'll see what happens.

 

[justin_o_guy]

Power brakes suffer the same fate. Light pressure on the pedal will allow the pedal to slowly fall. That's a failure inside the master cylinder. Your clutch lever drives a piston into the bore, displacing fluid and that fluid has to go somewhere. It goes into the slave cylinder which presses the clutch pressure plate open. The continual pressure the clutch is putting on the slave cylinder is shoving the fluid back towards the master cylinder. Anything less than a perfect seal will eventually allow the slave cylinder to relax enough for the clutch plates to start to engage. A seriously leaky master cylinder may only disengage the clutch for a few seconds, or, if it's bad enough, not at all.
CAN the slave leak internally? I couldn't say.