I have an early 80's schwinn road bike that I have converted single speed, but I am having chain tension issues.
The bike is equipped with semi-horizontal dropouts so I am not running a chain tensioner. As the crank spins, the chain gains and loses tension. It's not enough slack to cause the chain to skip, but it is pretty close.
I have inspected the chain and there are no stuck links so I ruled out the chain. I swapped out the crank and chain ring and still the same issue. I swapped the bottom bracket and that didn't fix it. The tension changes whether I am pedaling forward or spinning backwards with the rear wheel stationary.
I have tried everything I can think of, but I have gotten nowhere.