ive converted it to a single speed due to the fact that some components were in not so great shape.
i have spun the cranks with the chain not attached, they move fine.
i think its because the crank arms are too short for the 27 inch wheels i put on it.
i added a new chain, so thats not the case.
i noticed it was easier to get going on 24 inch wheels than 27 inch, which is why the crank arms smaller