Clutch Slave Cylinder

[TheBlueStreak]

I don't think that there is any difference with the piston of the slave or it would have another part number. As I mentioned before, I have squeezed the clutch of a 2009 at a MC show and it is lighter than a 2008. So I think the slave change is what is making the difference since nothing else has changed with the 2009.

I would like to hear form some 2009 owners to find out how close the engagement point is??

 

[Fred W]

Hydraulic systems, like brakes, are self-adjusting. The piston to rod engagement point is "0" once the system is "pumped up".

Good point. So then that only leaves a difference in the clutch itself or possibly the master cylinder is different.

 

[RadioHowie]

Hydraulic systems, like brakes, are self-adjusting. The piston to rod engagement point is "0" once the system is "pumped up".

Good point. So then that only leaves a difference in the clutch itself or possibly the master cylinder is different.

So my question...is the Gen 1 slave piston larger in diameter than the Gen 2? Or vice versa.

I'm no fluid dynamicist, but logic tells me that if you replaced a small bore cylinder with a large bore cylinder, the same amount of fluid applied within that cylinder would move the larger piston more easily, since the fluid is acting on a piston with more surface area exposed to the fluid.

However, since the amount of fluid being injected into the cylinder by the clutch master remains the same, and the force necessary for moving the piston would decrease, there would be less travel of the piston, thereby less disengagement of the clutch, thereby the re-engagement point would be closer to the grip.

Methinks there must be a difference in volume supplied by the master cylinder on a Gen 1 to compensate for the larger bore piston in the slave cylinder. Anyone checked the part # differences on the clutch master cylinder for comparison's sake?

 

[Fred W]

So my question...is the Gen 1 slave piston larger in diameter than the Gen 2? Or vice versa.
I'm no fluid dynamicist, but logic tells me that if you replaced a small bore cylinder with a large bore cylinder, the same amount of fluid applied within that cylinder would move the larger piston more easily, since the fluid is acting on a piston with more surface area exposed to the fluid.

However, since the amount of fluid being injected into the cylinder by the clutch master remains the same, and the force necessary for moving the piston would decrease, there would be less travel of the piston, thereby less disengagement of the clutch, thereby the re-engagement point would be closer to the grip.

I believe it is exactly as you have stated it. That is why the 1st gen slave provides easier lever effort.

Methinks there must be a difference in volume supplied by the master cylinder on a Gen 1 to compensate for the larger bore piston in the slave cylinder. Anyone checked the part # differences on the clutch master cylinder for comparison's sake?

But if the 1st gen master was of a small enough diameter to equalize the larger slave cylinder's stroke, then there would be no mechanical advantage over the 2nd gen. In other words, they would cancel each other out from a lever effort standpoint.

 

[RadioHowie]

But if the 1st gen master was of a small enough diameter to equalize the larger slave cylinder's stroke, then there would be no mechanical advantage over the 2nd gen. In other words, they would cancel each other out from a lever effort standpoint.

I disagree. If the Gen 1 master cylinder pumps X amount of fluid into the slave cylinder, it will pump the same amount into the slave whether the slave cylinder is wide or narrow. The lever effort is going to change IF the slave cylinder/piston is wider in diameter. The effort will be reduced, but the amount of travel of the piston will be reduced as well, since the fluid is now having to fill a larger cylinder bore with the same amount of fluid. Easier, but less effective as far as travel of the slave piston is concerned.

So the only way to reduce effort, while maintaining the same amount of piston travel is to have a larger bore slave, but pump more fluid into the slave.

All of this is moot, however, if one assumes the Gen 1 master and Gen 2 master inject the same amount of fluid into the slave. Then the only limiting factor for disengagement of the clutch has to lie in the clutch itself....

...or God forbid, someone complaining of "tight" disengagment relationships between the lever and grip aren't aware that the lever is adjustable in its distance from the grip. If THAT'S the case, we should shoot them now.

 

[Fred W]

But if the 1st gen master was of a small enough diameter to equalize the larger slave cylinder's stroke, then there would be no mechanical advantage over the 2nd gen. In other words, they would cancel each other out from a lever effort standpoint.

I disagree. If the Gen 1 master cylinder pumps X amount of fluid into the slave cylinder, it will pump the same amount into the slave whether the slave cylinder is wide or narrow. The lever effort is going to change IF the slave cylinder/piston is wider in diameter. The effort will be reduced, but the amount of travel of the piston will be reduced as well, since the fluid is now having to fill a larger cylinder bore with the same amount of fluid. Easier, but less effective as far as travel of the slave piston is concerned.

So the only way to reduce effort, while maintaining the same amount of piston travel is to have a larger bore slave, but pump more fluid into the slave.

All of this is moot, however, if one assumes the Gen 1 master and Gen 2 master inject the same amount of fluid into the slave. Then the only limiting factor for disengagement of the clutch has to lie in the clutch itself....

...or God forbid, someone complaining of "tight" disengagment relationships between the lever and grip aren't aware that the lever is adjustable in its distance from the grip. If THAT'S the case, we should shoot them now.

Think again, Howie. It's the ratio of the volume of the master cylinder output to the volume of the slave cylinder that would determine and effect both the effort at the lever and inversely the distance of the slave cylinder stroke per unit distance of the master (lever).

 

[PA1195]

My plan is to order and install a GenI slave cyl on my '08 and test. I'd like an easier clutch, do to an old damaged thumb joint.

I'll bet the GenI has a larger potential cavity, accepts more fluid, and moves less per unit travel of the master piston than the GenII.

Simple lever relationship: more travel of the master per unit change in clutch engagement = less effort to move the lever.

We'll find out next week.

Gary in Fairbanks

 

[TheBlueStreak]

As it turns out the master cylinder is the same on the 2005, 2008 and 2009. So again, it all boils down to the slave cylinder!

 

[Fred W]

As it turns out the master cylinder is the same on the 2005, 2008 and 2009. So again, it all boils down to the slave cylinder!

How about at the other end? Maybe the clutch itself is different somehow?