Andy VH said...
When you consider the limited amount of fuel most bikes carry, and the fact that the fuel/water in the tank are not exclusively separate volumes, and that in most bike fuel tanks the standard fuel pickup tube in the tank is not much higher than the reserve pickup tube, its really a moot point. The "reserve" in a cycle fuel tank is not a separate section of the tank, nor is it a lower/lowest section of the tank. The reserve pickup tube is simply a lower level in the tank than the standard pickup tube. As a bikes bounces down the road, and as it leans through turns, the gas and water are mixed to a point.

When the bike is shut down and stationary, then the heavier water in the gas will settle to the lowest point, which is likely lower than the reserve pickup tube level anyway. If it weren't, then you may have starting problems when that water gets into the carb or fuel injection system. Yamaha proved that on the 500cc Vision, which had deep pointed sections on the lowest portion of the fuel tank. Rusted fuel tanks and fuel contamination are common issues on the Vision. Most riders park their bike on the sidestand, which is usually opposite the fuel valve side. That means, IF the fuel tank doesn't have a deep/tall tunnel, that water in the tank is probably collected on the left side of the fuel tank. Of the fuel tanks you have seen rusted through, how many have you seen rusted through on the fuel valve side of the tank?

Probably a better practice is to run a bottle of HEET through the fuel tank about once per season. Consider too that most cycles spend most of their time sitting and only run once a week, a few times a month, so they are more likely to have fuel/water issues. If you regularly ride your bike, three to seven times a week, and frequently pour fresh fuel into the tank, there really is no water issue. That's yet another reason to ride your bike more often. More riding, more miles, is far better for a bike than letting it sit unused for most of the time.