odd clutch behavior -- air in the line?

[Dr. D]

About four weeks ago, while at Summit Point Racetrack, the clutch began slipping badly.  When applying heavy throttle the engine would spin up while the bike slowed down.  Easing off on the throttle, the clutch would catch with some jerking.  Little to no engine braking. 

Due to other activities I didn't touch the bike until yesterday when I took it out for a local spin.  Clutch behaves normally.

When I talked to the shop about this, before the local ride, they said it might be air in the line instead of a fried clutch.  Would this behavior (especially the clutch working normally again) fit that?  The bike has only 4,500 miles on it.

[Howie]

More likely too little free play at the lever or you just overheated the clutch.  Lever free play should be 1-1.5mm.  An open cover would help with overheating.  Air would lead to the opposite problem.

[Slide Panda]

Air in the line would not do that - it'd sort of be the opposite. Air just compresses when you pull the lever, as a result the clutch won't disengage. Common symptom of a clutch that needs to be bled are jerky low gear low speed shifts, and a lot of troubles finding neutral if the bike is not rolling.

As Howie mentions, it's more likely there's something adding pressure to the system, that causes the clutch to partially disengage. IF there's not enough free play, the fluid return port can get partially or fully blocked. Then the fluid heats up and expands it'll push the pressure plate out. Wet (water saturated) fluid would exacerbate any issues like this as it lowers the boil point of the fluid.

[ducatiz]

When I talked to the shop about this, before the local ride, they said it might be air in the line instead of a fried clutch.  Would this behavior (especially the clutch working normally again) fit that?  The bike has only 4,500 miles on it.

a shop suggested this?  uhh...

no.

as previously said, air would prevent you from disengaging the clutch.

do you have a wet or dry clutch?

if you have a dry, take the cover off and inspect to see if you have any oil coming thru the seal.  oil can penetrate, get on a plate and then get cooked/spun off.  this is not likely due to the age of the bike, but i have seen seals installed backwards from the factory.

how experienced of a rider are you with this bike and bikes in general?  if you are relatively new, it's possible you burned the clutch out. 

are you the first owner of this bike?  prior owner a clutch burner?

[Howie]

DOH   696?  Forget the open clutch cover.

[ducatiz]

DOH   696?  Forget the open clutch cover.

yeah...    i always forget to look at their sig too

[Speeddog]

Aftermarket clutch lever?
Possibly no freeplay and thus the bleed port blocked.

[Dr. D]

Aftermarket clutch lever?
Possibly no freeplay and thus the bleed port blocked.

The bike does have aftermarket levers, but they appear to have sufficient play -- I will look at that closer.

There are signs the (two) POs were a bit hard on the bike.  I changed the brake pads at 4k miles and the old ones were worn way down.  I got a great deal on the bike!

Experience:  10+ years, multiple bikes, 12+ track days....  I don't think it is me.  But then, who does?

New thought:  Insufficient free play would apply to a hydraulically actuated clutch, too, right?  I checked and there did not appear to be any free play.  Fixed (if that was the problem).

[Howie]

The bike does have aftermarket levers, but they appear to have sufficient play -- I will look at that closer.

There are signs the (two) POs were a bit hard on the bike.  I changed the brake pads at 4k miles and the old ones were worn way down.  I got a great deal on the bike!

Experience:  10+ years, multiple bikes, 12+ track days....  I don't think it is me.  But then, who does?

New thought:  Insufficient free play would apply to a hydraulically actuated clutch, too, right?  I checked and there did not appear to be any free play.  Fixed (if that was the problem).

Insufficient play will block fluid from returning to the reservoir, eventually causing partial disengagement.  Heat build up makes it worse.