The fork spindle on the 400 is over 1" in diameter, that's the measurement I was worried about, I just assumed since it was a metric bike, it would have a smaller diameter neck than a Harley (guess I shouldn't assume). It tapers down to 1" at the end (top) and there is a company that sells the adapter for the Harley forks (brings the bottom down to 1" diameter) and is advertised to convert "all early model Yamahas" to accept a Harley forks. I am going to try this route and see how it works out, can't hurt I suppose. I am determined to convert the front of my bike to a springer, since it fits the bobber motif so well.