[Noriyasu]

Yes, it could be bad gasoline. In that case, when you remove the fuel filler cap, it smells different than usual. Japanese high-octane gasoline usually does not cause problems for about half a year.

If you have a problem with gasoline, I recommend draining the old gasoline from the tank before you replace the fuel filter.

The filter is placed in two place. One is in engine room. and other is attached on fuel pump in fuel tank. The genuine fuel pump and packing are discontinued. I do not recommend removing this. You will need to access from fuel filler port to remove old gasoline because there seems no drain bolt at bottom of tank.

The filter in engine room can replace easily. But, usually fuel hose will deteriorate and become stiff. If you haven't replaced it recently, it's a good idea to prepare up on fuel hoses.