Clutch Woes

Anyone who can help -

A while back I replaced my hydraulic clutch line with a steel
braided line. Prior to this, the clutch had been bled my myself on
one occasion. Since the bike was used, I don't know if it had ever
been bled previously (probably not).

Since I have replaced the line I have had a problem with the
clutch. It's not consistent and this makes it even harder to
troubleshoot.

What happens is that I can ride the bike for a few weeks and
quite a few miles (doesn't appear to be time sensitive). Then, I'll
be on a long ride (or at least it always happens on a long ride),
everything will be fine, and then my ability to engage the clutch
greatly diminishes.

The last time this happened I was on a pretty good ride and
everything was fine up until I was on the way home. We decided to
slab it down I-20 since we were a good ways out. No problems at this
point. Then, we went to exit on I-20 and I started to downshift - no
clutch, or very little. I was able to move my lever to the most
outward position to gain a mechanical advantage and get the bike home.

So this has happened about three times. In all three cases I
cannot detect any leakage around the line, the banjo bolts, or the
washers. I also took a flashlight and checked the line to see if any
fluid had pooled up inside the line between the clear shielding and
the line itself. If I bleed the clutch it works fine again until some
undetermined amount of time or mileage. I can't figure out which one
seems to be the key factor (if either).

Theoretically, if there was even a small amount of a leak the
pressure required to engage the clutch is greater than the outside air
pressure and it should have leaked outward rather than let a bubble
in.

In any case, the closest thing I have found to a leak is that
I think the seal on the reservoir may be leaking as I found some fluid
had leaked out, but I couldn't be absolutely sure this didn't happen
last time I bled the clutch. And, while I am no master of hydraulic
systems, I wasn't sure this type of a leak would affect the
performance as no air could get in the line (i.e. your brakes and
clutch work fine without the caps on the reservoir). Unless, that is,
the fluid became ruined by contact with the air and lost it's ability
to not super-heat.

Anyway - I am a bit stumped and need to try to fix it so if
anyone has any good suggestions I am all ears.


--Fullstate

Me and Mah 'Priller!

 

This strikes me as being more temperature related than anything, as it
is the long sustained run that brings on the symptoms. A guess would be
a small amount of moisture is trapped in the system since you are
finding no leaks. When it gets hot enough, as in a sustained run at
speed, it boils into vapor which is then more compressable than as a
liquid. When you compress the line for clutch action, the vapor
compresses first leaving you with little hydraulic action on the clutch
mechanism itself. Try draining the entire clutch hydraulics, refilling
it completely with fresh fluid and see what happens.

 

Fullstate,
You've hit one of my favorite clutch problems - the kind that changes!

A couple of ideas - since it seems to be temp related, you may be
boiling off some water somewhere in that system, resulting in a clutch
lever that is non-functional. I'd try bleeding all the fluid out,
preferably with some sort of vacuum system (not pumping it out) -
replace it with a good synthetic brake fluid.

I've seen late model Camaro/TAs with this issue - they tend to boil
their clutch fluid as the MC is actually buried on the inside of the
transmission on these cars. A few good burn outs and you won't be
able to shift until things cool down. Another mod is to drill out the
smallest point in the hydraulic system of these cars - I don't think
I'd try this right off the bad though.

I'd be surprised if you were boiling the fluid, but wouldn't be
surprised if you had some ancient water in that system somewhere.

 

Thanks for the tips and advice. I will certainly try bleeding the
clutch again. I've probably bled it about three times since I
replaced the line and every time I use DOT4 brake fluid and make sure
that I completely flush the line.

I haven't drained it, filled it, and bled it, though. Perhaps that
will make a difference.

Oh, as for temp - once this does occur it does not go away once the
bike has cooled down. The bike can be stone cold and I can't use the
clutch until I bleed it again. It also does not seem to occur once
the bike is warm since I get the bike up to temp for long periods on
regular flogs. Just a thought.



--Fullstate

Me and Mah 'Priller!