Speed change after replacing blade

Do you know of your old blade may have been a thin kerf blade? If so it would have been a lighter blade which would have less drag on the motor at start up. Or if you had a different brand blade that may also have been a lighter weighted blade in comparison to your new one. If your saw is showing no other issues while cutting and it's only a matter of a little slower start up it may just be an issue of what I described. Over tightening wouldn't be an issue. Just keep your eye open for anything that doesn't seem right while cutting like new vibrations or movement while cutting as that would indicate bigger /serious issues potentially.