I am trying to get an old Rampar R1 back on the road as a fixed gear…no loss since it’s just a Rampar. I thought it would be pretty straight forward till I got to the crankset. I ordered a generic crankset from ebay and the listing said it was for JIS square tapered bottom bracket. My R1 still has its original SR crankset and I thought it was JIS. Today I received the generic ebay crankset and it didn’t come close to fitting on what I thought was my JIS bottom bracket. The original SR crankset slides right in sooooo easily but the new crankset won’t fit at all…way smaller. Could the original SR crankset be ISO instead of JIS?

Well, you'd have another problem, even if it fit. The original spindle is for a double chainring, and the single speed crankset will need a shorter one. You can get a basic Shimano cartridge bottom bracket for very cheap, and it might be a good option for you.

thanks for the reply, that sounds like a good idea. Now should I expect a shimano cartrige thats 68mmx103 work? I'm worried that I will get it delivered and it still wont fit my generic crankset. Could my original bottom bracket spindle be ISO?

I'm not sure about the SR crankset, but it doesn't much matter if you're going to use a new one and need a new BB too. You should check the specs from the manufacturer about spindle length, but 103 is probably in the neighborhood. Given that the bike is a Rampar, English thread should be right.

Thanks for the advice, I will try my luck with a shimano cartridge for my new crankset.