Holy sludge Batman!!!!!
I wanted to change over to the newer style fuel tank so I dug one out of the pile . I shined a flashlight through it and it looked clean and had no smell. Was I wrong . It ran great for a quick run and the next day the new filter turned coffee brown. The quad would no longer fire. Apparently when the tank was removed some 15 years ago it still had some fuel in it and was sitting upside down so a thick tar like substance formed on the roof of the tank. It could not be seen from the bottom where sediment usually is easy to see through the plastic. It didnt disolve until I put enough gas in the tank to reach the sludge. Now I get to clean my new injectors and fuel lines. The filter in the fuel pressure regulator was plugged.