The wheels do spin freely and it starts fine. It lacks power and I remember it stalling when I stop. I think the chain is fine. I seem to remember the mechanic fixing the slack. Unfortunately I don't have the same knowledge about bikes as most people on here do. I have learned through having to take things apart and guess. How do I do a compression check? The airbox, if that's the air filter, is also fine. I have good spark as well.