Can i use a thinner standard mtb chain (SRAM 971) or does the chain need to be specific (SRAM PC-1) for coaster brake single speed Time for a replacement chain, and i have a sram 971 sitting around, don't want to spend the money on a new chain, if i can get away with using a mountain bike chain. Hopefully it won't pop off with standard tension?
Your cog is probably 1/8" like that PC-1 chain, so that 3/32" chain isn't going to work. Let's say you could even get it to fit in the first place, it would probably pop off at the least convenient moment, like when you're trying to stop with that coaster brake.