'99 Valk Hydraulic Clutch

[Ratdog]

Bike's been parked for a couple of years now. Dragged it out, slapped a new battery in it and took it for a test spin. Got some Lucas Fuel System Cleaner and some SeaFoam in the tank with a fresh load of fuel (getting "more gooder"). I'd forgotten how HARD this beast pulls when those six carbs start sucking hard. LOL

 Rode it to some training for a new job (about 25 miles away). Not too bad going (morning/chilly). Coming home, it'd warmed up considerably. I noted that the clutch began slipping under a load, but then would grab and settle in. Soon, it started slipping a little more. About halfway home (stop/go rush hour traffic), it didn't want to grab any more. I also noticed that the worse it slipped, there was a change in the clutch lever (hydraulic). It eventually would only pull about halfway and it felt like I hit a wall. If I pulled really hard, I could pull the lever further back (normal is to easily come back to the bar's grip).

 I let it sit for a while, and it started to grab once again. I pulled into a parking lot and went in to get a cup of coffee and let it just sit and cool off for almost an hour and a half. The clutch was grabbing better again, and the lever felt better too (pulling further back than it was). By the time I got home, it was beginning to slip again, and the lever was only pulling about halfway and felt like it was hitting a wall. This morning, the clutch lever feels "normal" and easily pulls to the bar's grip.

 I've ordered up a master cylinder rebuild kit for the clutch. My deductions are that sitting for so long, I got some moisture in the system and (as a result) some corrosion going on. The flow of hydraulic fluid isn't as it should be within the master cylinder. But, sitting, the pressure balance is eventually evening out. I'm not (at this time) suspecting clutch discs being trashed.

 Having sat for a while, the fluid is darker than I normally allow. I've generally (when riding often) changed the fluid (always been synthetic) when it's about the color of weak tea. This spring, it's looking darker, between tea and coffee in color.

 Bike's got 141,000 miles on it now (after 15yrs. worth of ownership). I've already got Speed Bleeders installed, as well as braided steel lines. Engine oil was changed last fall before being put up for the winter.  Same M/C specific oil I've used for 141,000 miles.

 Anything I may be overlooking in my diagnostic exercise?

[The emperor has no clothes]

It sounds like the clutch rivets might be giving way.

[gordonv]

The last thing I would start with is replacing the master cylinder. Change the fluid. Do an oil change on the bike (if you already did, check the oil for the right mc type).

You start by asking here. I also thought rivets on the clutch, but haven't followed the systems enough to know if you are having the same signs.

But the oil change is easier and cheaper first.

[Ratdog]

The last thing I would start with is replacing the master cylinder. Change the fluid. Do an oil change on the bike (if you already did, check the oil for the right mc type).

You start by asking here. I also thought rivets on the clutch, but haven't followed the systems enough to know if you are having the same signs.

But the oil change is easier and cheaper first.

The rebuild of the master cylinder will be phase 2 of the process.  Flushing with fresh fluid will be step one.  I use full synthetic DOT 4 fluid, have for 141,000 miles now.

Engine oil was new/fresh when I put it up last fall (including filter).  I'm not concerned whether it's the right oil... same M/C specific synthetic oil I've been using for 141,000 miles now.

[Dusty]

 I  would also blow out the lines with compressed air. It sounds like a blockage somewhere in the system and that causes your lever to not move all the way. The blockage may also stopping your fluid returning to the master so that's where the slipping comes from as the slave doesn't retract.

 I can also see that a rivet issue could cause the same symptoms. If the slave  can not fully extend because of jammed rivets the clutch lever will go hard .

It comes back to normal after sitting overnight points to  debris floating around inside the fluid and not rivets .

Let us know what you find

Dusty

[Highbinder]

Charles, I had the same problem a while back...the return line to the master cylinder was clogged....clutch was fine until it warmed up and then it started slipping.  The fluid would heat up in the line and put pressure on the slave clutch causing it to start slipping...I cleaned out the master cylinder, disconnected the banjo nut and blew out the line...put it back together and everything worked fine...sounds like the same problem.