So, While I wait for work to be done on my Ducati, I have been riding my Wife's 400 Twin (Honda CB400t, 1978, Hawk). I have noticed that it has a surge to it as you ride down the road. It feels like something in the drive line. If I put the bike on the center stand, I can spin the rear wheel and I notice no tight spots on the chain, The rear wheel spins true and doesn't seem to out of round or anything. The rear sprocket looks to be fine. Where else should I look on this?