I'm glad I took my flywheels off. If not, I never would have figured out some of my ballance issues. The cast in weights were NOT the heaviest part of the flywheels. When rolled on a smooth surface (on a 2" shaft would have been better, but I didn't have one), the flywheels would stop with the weight at about 5:00 instead of 6:00. I had to take many slow hours with an angle grinder and slowly remove extra flash from individual spokes, and areas around the inside of the rim to get the flywheel weights to point straight down. Without even adding or playing with other weights, the engine ran MUCH smoother after that. I have no idea how much weight was at each location, and with enough effort, I could have gotten it smoother than I did, but on a cubic yard of concrete sitting on a 1/2" rubber mat, it worked well.