Remove/rebuild the carbs and change or clean the inside filters. Also look at the big semi clear filter near the front for any debris...it just unscrews, but might drip gas so be careful. If rebuilding use only OEM carb parts.
The gray lines will decay inside due to the ethanol in the gas. It makes a green goo that plugs up everything, including the carbs, filters, and fuel selector knob (ON/Reserve/Off). replace and clean everything