In no particular order: Do you think it's done this ever since the work? Visual inspection from filler cap to exhaust: filler hose, fuel tank, float fitting, pipes... do you have an Assembly Guide? If the tank (or anything else) is dirty give it a good clean and then inspect again. You can use bits of paper towel to check for moistness. Get someone else to confirm the timing of the appearance of the smell. Starting and running OK? Any visible emissions from exhaust pipe? Does it live in a garage or outside? How far are you from the remapper, and where are you?And the safety note: keep everything well ventilated, no naked flames, pilot lights, smoking etc and have a fire extinguisher somewhere appropriate. Jonathan PS: Any pointers and as I'm a complete novice, please provide as much detail as possible. "We are all complete novices, but some of us are looking at the stars". :-)