when it is at TDC all three of the internal markings are aligned but the exhaust valve is open just a bit at TDC. I don't know much on how it ran before I took it apart. I bought it for 800.00 and was going to change rings cause of smoking then found more problems I have maybe 1200-1300 in it now. I did test drive it and drove it around the yard a few times before I decided to take her down to keep from messing anything up worse. All it does now is backfire and I didn't do anything to the valve or valve springs