So, I have a 250K pot and I need a 100K; is there anyway I could throw a few resistors on that to make it 100K? If so, what values?
Yes there is. Adding a resistor in parallel will lower the resistance of the potentiometer circuit.
Using: R-total = (R1*R2)/(R1+R2) you get the following:
100K = (250K*R2)/(250K+R2)
R2 ~ 167K
Of course you will probably need to use a few more common value resistors that add up to 167K in series.
Feeling extra bored so I made you a diagram.
(http://imgur.com/aPgov.png)
That will *kind of* work, but will make the control law pretty non-linear.
If the 250k pot is wired as a potential divider rather than just a variable resistor, its value might not matter much. If it *is* wired as a variable resistor, it might just give you a useful range that's all up one end, or it might make things even better. Without seeing the circuit it's hard to tell.