I have this old Sekai that I got to turn into a singlespeed. Pic >>> http://img20.imageshack.us/img20/3071/p1010386r.jpg. It came with a cottered crankset. I'm looking to spend as little money as possible, so at first I was just gonna use it and keep going. Then I realized that there was a little movement between the 2 pedals. I took the crank apart. I'm assuming that the wiggling was occurring due to a messed up cotter pin. So I need some advice, should I 1. Get a new cotter pin ($4), or 2. Get a new crankset. Problem with #2 is that I don't know what kind of bottom bracket I'd need to get, and I'd like to spend $20 tops for crankset and bottom bracket =/. Anyone know their Sekais? Thanks for reading.

PS: Bottom Bracket stamp reads "18072" or "78072", can't really tell. Hope this helps!