If you've got any old stereos, tape players, portable cd/tape players, etc., just sitting in a junk closet, then you already have at least one log pot laying around waiting to be tested.
Unsolder the volume control pot and you've got what you're after. It will probably be a 10Kohm or 100Kohm pot, stereo so that it has actually two 3-pin pots in parallel. If it's a 10K and you want only a 5K, you could solder across each pair of pins, for the end taps of one end, the wipers, and the other end taps, although it won't be a perfect parallel because many pots are not exactly identical all the way around--but it will be very close.
So you could use that to test for the behavior you want, on a "bench stand" (upside down bike with wheel in air, for instance), before you try rigging one up into a throttle control unit.
Some of the pots will be slide pots, rather than rotary, which might make an interesting throttle.
I did actually try this on the ScootNGo when I was first getting into controllers, but I never got it to work right, because it was after a Hall type voltage range rather than 0-5V and I did not know about that at the time. If I had known, I would have calculated out what resistor values I needed in order to make a voltage divider setup with the pot in the middle so it had the full adjustment range expected by the controller from end to end, with the rest of the voltage across the end resistors in series with it.
