6th Sep 2017, 18:05
I had that problem with my Yamaha 750 Special. Turns out it was a hole (split) in a fuel line that only spouted when the RPMs were up and I was going faster than 50mph. Any thing below that was fine. Changed the lines and it was fine.
26th Aug 2015, 01:24
It sounds like your vacuum petcock has failed. Very easy fix (and cheap too). Check out Suzuki Savage dot com. Those fellows know more about the S40 than Suzuki does.