Potentiometer for Expression Pedal?

[intergalatico]

Hello Folks,

I have a Bespeco VM 18L Expression Pedal: http://www.musicstore.de/en_EN/GBP/Music-Store-VM18L-Volume-pedal-switchable-/art-ACC0000012-000

I want to use with my Roland Gr-55 but it have to be a 50K pot instead of the 20K inside. I make the change but I notice that the original pot (20k) moves only until about 1/4 of the whole spin. So when I put the 50k pot inside, the mechanical movement from the foot controller spins the pot only like 1/4 and so I didn't achieve the whole 50k value from the pot. Consequently I can't have a 100% parameter value.

My question is:

1. How is called such a only 1/4 spin potentiometer? Is easy to find? I live in germany, so if someone have a store advice would be great! (I searched about this pot like crazy but without results. Maybe because I don't know how to call it)
2. If I can't find a pot like these, can I use a 200k pot and assume that the foot controller will achieve only the 1/4 of the 200k? (=50k)

Thank you very much for your help, guys!

Chers 

[antonis]

Assumption No2 is true and correct BUT the result depends on pot position in volume circuit...

If it's at the end, acting only as a variable voltage divider, you may notice an overall volume drop because of the increased pot resistance..
(especially at low settings - which is exactly your case..)