Last year, I had a Devil of a time getting the clutch on my 1990 FLHTC Electra Glide working correctly. In the process of getting it sorted, I learned more than I need to know about how the overall system works.
The system starts with the clutch lever itself. It is, literally a “lever”, meaning that it both multiplies force and reduces travel. I don’t have the measurements with me at the moment, but if you call the distance from the handle to the pivot point “A”, and the distance from the pivot point to the cable attachment point “B”, then the lever multiplies force by (A/B).
Then the level pulls on the cable. The transfer of motion from one end of the cable to the other is only effected by the friction of the cable sleeve. If you want to get an easier pull, the only way to do so without effecting clutch performance is to reduce friction in the cable. There are supposed to be better cables out there. When I put my new handlebars on, I went with a Barnett unit.
From there, the cable pulls on the “ball and ramp” mechanism, which looks like this.
As simple as that looks, it is actually a fairly sophisticated, compound lever.
As simple as that looks, it is actually a fairly sophisticated, compound lever. There is lever action based on the distance from the hook to the center (A), as well as lever action (this is the ramp part) based on the shape of the wells that the ball bearings sit in (B).
When the clutch lever is pulled, the cable is pulled, which in turn pulls on the hook shown on the ramp mechanism. That causes that side of the mechanism to rotate, which causes the ball bearings to spread the two halves apart, creating the final motion that drives the clutch rod.
In the “normal” state (ie, the clutch lever not pulled in), the two halves of the mechanism lie pretty much right next to each other.
When you squeeze the clutch lever, it causes the top part of the ramp to rotate, which causes the ball bearings to force the two halves apart. In this shot, I am showing the action in a highly, highly exaggerated form. In actual operation, the total amount of movement is less than one tenth of an inch.
These are the crap 15 degree units that I pulled out of my bike. I replaced them with 21 degree units. The 21’s give greater clutch throw, which gives better operation, at the expense of having a harder clutch lever.
What’s All That Mean?
Boil all that down, and this is what you get: If you want to reduce the amount of force on the clutch lever, the only way to do so is to either modify the mechanism in some fashion, or to reduce friction with a better quality cable. Any modification to the mechanism will, by definition, trade off easier clutch lever action for less clutch rod movement, which can have negative effects as well.
There are various “easy pull” systems out there. Some (like the ramps shown here) achieve their easy by having a shallower angle on the ball and ramp.
Other systems have some manner of dongle that attaches to the hook, effectively increasing the lever distance “A” as shown above. That means that for a given clutch pull, you will have less rotation, and therefore less displacement in the ball and ramp, but the amount of effort will be reduced.
There are probably clutch levers available that have less lever action as well. Never seen them.
You can also put in easier clutch springs, with the tradeoff that less spring force means greater chance of clutch slippage.
Bottom line is you can not get something for nothing when it comes to these mechanisms. The only tradeoff-free solution is a lower friction clutch cable. Everything else is a compromise.