I have used seafoam on some older bikes. I did notice the motor running rougher til that tank emptied. Some had said may break loos crude, rust or so in the tank. Not sure really what causes that.
On a different Honda forum, we found the rougher running motor was due to " a little is good, more is better" attitude. Mix by the suggested ratio and run several tanks through. Should be kinda quick on the Valk. The ST is a ~300 mile tank bike (7.4 gal. @40 mpg).