Just trying to make sense of all this stuff about belt squeeze - I understand fully that more pin weight will create more belt squeeze, but where I become confused is when you start adding different primary springs into the equation.

If I'm running stock clutching in my 800 MXZ, I have a 160/230 primary spring and approx 16.7g of pin weight. I understand that if I go to 18g pins with this set up, the rpm's will come down and I should get more belt squeeze, right?

So now what happens if I go with 18g pins and add a 160/270 primary spring? Does this not then take me right back to the same amount of "belt squeeze" I originally had with the stock set up since I've now just countered the heavier pin weight with a stiffer end load spring?

It seems everyone uses a 200-290 spring with 18.5g pins.Heavier pins will upshift faster.

I am going to offer this explanation.
The higher the force of the spring the more force you will have to apply to the clutch to get the same belt squeeze. This is true for both initial and final spring forces. The final spring force directly affects your max RPM. An effective method of tuning your max RPM is by changing pin weight. Increased pin weight= increased force opposing spring=higher belt squeeze=more load on motor=decreased RPM. The opposite is true if you reduce pin weight.