Bill,
I would never want to. Low gear is too high now. I'm constantly having to working the clutch in low speed traffic.
And when you're short on hp for hi speeds, you don't gear higher!
But I have stuck a piston before from running too tall gears, and that was after bigger main jets. My s-40 is not spinning too fast at 50-55 by any means, which is about the max speed I normally ride. If yours is, then change the gears to chain.
Are you sure you have a 5 speed, or is it going into 5th gear ?
I've read where many s-40's change to lower gears to pick up top speed.
Me,....I need a tac-o-meter !