Hello, my problem is my ys 91fa was running well then it started surging. It will idle all day, but over half throttle rpms will drop 50% in about 5 seconds, for 5 seconds,then return to high rpm. Using ys fuel, f plug. Any ideas?
Thanks, venom

Could be something leaking. Check all the bolts.

Just a quick note. I had a leaking fuel filler on the pressure side. All is well.
venom

Good