Water Warrior is correct in his last post. Apparently, moving the pivot hole in the lever by a small amount causes enough of a change in geometry when the lever is pulled that the pull becomes much easier.
That is only the secondary benefit, though. The primary benefit is claimed to be that the change in geometry causes the clutch to begin to engage when the lever is closer to the handle. This apparently widens the friction zone so you have more space with which to control clutch engagement. If you look at the before and after pictures on the Clevver site, you will see that on the stock setup, the point of the start of clutch engagement occurs when the lever is roughly 20 degrees beyond parallel with the handle. With the Clevver, the point of engagement occurs when the lever is roughly parallel with the handle. In both pictures, the end of the friction zone appears to be roughly in the same place and the free play zones seem unchanged as well. Looking at the pictures and seeing the visual result of the change of geometry seems to lend credibility to the claim of a wider, more precisely controllable friction zone.
This solution was developed for a particular family of bikes from a single manufacturer. These bikes are described as having clutch levers that operate like on-off switches. The solution claims to provide more fine-grained control. It appears that the guy who makes these makes them out of OEM handles. Perhaps he is able to get them from Yamaha without the pivot holes pre-drilled. Curiosity has got the best of me - I've ordered one and will post pics when it arrives.
In the meantime, here is a link to a long thread discussing the device.
http://www.yamahamotorcycleforum.com/fo ... 669&page=1 This is where I read that Moto-Cross riders have done this mod to their bikes on their own for a long time. I'm not sure if you have to sign on to read. Moderator, apologies if posting this link is inappropriate. I checked the protocol post and didn't find a prohibition. If it is inappropriate, I completely understand your deleting the link.
And my question to the community remains: Might this principle be applicable to a GZ and perhaps make an already nicely ride-able bike even more so?