I got my 1981 XS 400 for free. The owner had ran out of oil down while driving down the highway, most likely with the tachometer pegged in the red. I put a 1977 XS 400 D engine onto the 1981 XS frame. The bike is damn near perfect now, I painted it, replaced the chrome and lowered the bars. It is a very fun bike to drive because the lowered stance feels like a sport bike. Here are my gripes. The bike with 15,000 miles on it runs like a top, but has much less stomp than my HONDA CB 360 (which is smaller #@%**). The compression checks out, the carbs are absolutely dialed, the timing isn´t a hair off and the power is horrible. The stock exhuasts don´t help matters. But 80mph is a joke.. If you can sustain 80mph against a 2mph wind you are lucky. I have had the speedometer up to 85mph, but this was down hill! The bike is torquey in the mid range is a blast to drive through town. Its a beautiful bike too, lots of people look at it.. If you own a 400, be sure to run synthetic oil in it, as the upper end of the XS 400 engine is built rather cheaply in comparison to other bikes. If you have any other questions about the XS 400 (SOHC) you can email me if you´d like. Charles