I have a Norco Havoc which is a single speed. I recently took of the chain wheel to replace my crank arm. When I put everything back together on the bike, it seemed like the chain wheel was "lop sided". When I turn the cranks, the chain would go tight and than get loose and than go tight again, just in a few revolutions, and keep going like that. So I took it off again and tryed to put the chain wheel in stright. This time it wasn't as bad but still not good. Anyone got any soulutions to this problem? Thanks?