Who could rewind my outrunner?

[Metallover]

I am working on my e-bike project. I picked up a 100a suppo esc from hobbycity along with a 250kv outrunner. It is wayyyy overgeared. Could somebody rewind it to a lower kv? About how much would this cost?

I don't know what kv I need either. I'll need to calculate the gearing. What does it take to figure out how chains and sprockets effect gearing? Is it just like a spur/pinion?

and since pics always help -




edit - tell me if the pics don't work. Might have messed them up.