Neat. The tungsten balls are a good idea as a tuning aid in conjunction with different spring rates and pre-loads.
I haven't messed with the Kawasaki versions, but the Yamaha is a nearly identical assembly and there are several springs available from the various years and models including the YZ250-X model for off-road riding (stiffer spring with less pre-load).
If you want to geek out on it, here's some of the math that governs the governor operation...
After reading your pipe tuning thread, I assume you'll enjoy this stuff.
You can measure the spring pre-load using a dial caliper and then measure the spring rate (k) using a postage scale, a fish-scale, etc.
Use Hooke's law to determine the pre-loaded force:
F = kx (where
F is force,
x is pre-load distance and
k is spring rate in lbs/in or N/m or N/mm, etc.)
The ramp angle is probably around 45°, but can easily be measured with a protractor. Divide the total included angle by two so you have the angle between the shaft-axis and one ramp surface.
Radial component of acceleration is:
a = ((rpm/9.5493)^2 )/rwhere
RPM is the
governor rpm and
r is the starting radius of the balls.
Use
F = m*a (
F force = total mass of all four balls times
a radial acceleration) to find the force of all the balls.
The actual force the balls push against the spring uses the tangent of the ramp angle
Θ.
The final formula using (m = mass, Θ = angle, rpm = governor speed, r = starting radius of balls):
F-spring = Tan(Θ) * m * (( rpm / 9.5493 )^2 ) / r
Friction forces and the mass of the valve-train can be measured with a small fish scale and compensated for in the spring pre-load or rate, as well as with different ball masses.
That conversion factor 9.5493 comes from converting RPM to radians per second. So it's 60 seconds divided by pi divided by two...
Rather than weigh the balls and divide by gravitational acceleration, it might be better to use a dial caliper and calculate mass from their volume and material density. That is, unless you have a high precision laboratory balance.
For the opening RPM (Set by flyweight mass and spring tension) you can do a dyno pull with the governor linkage disconnected and the valve safety wired closed, then do a second pull with the valve wired open. The two curves should generally look like the image below. You can target the optimum opening RPM as the cross of the two curves. It's theoretical, as it takes time for the valve to open due to static vs kinetic friction, inertia of the parts, etc. A lot of the YZ guys are adding shims (more preload) between the spring and thrust bearings to tame the hit.
If I'm going way to far with all of that, kindly ignore the post...
I realize not everyone is interested in going so in-depth with stuff that's so easy to tune by testing parts.
Hopefully I didn't include any major mistakes in all that....
