Thought this was interesting?
I have noticed that sometimes after refuelling my 1999 Hayabusa doesn't run so good. Its been tweaked and runs a Power Commander so maybe its a bit more sensitive to the difference in octane? You're talking about one litre of fuel left in the hose, which I suppose could make a difference?
I don't think its a big deal - more of a curiosity item?
Q:I have a motorcycle with a typical three to four gallon gas tank. I ride where fuel stations are farther apart, so I fill up when the tank is still half full. The bike requires premium fuel, and doesn't run well on lower octanes. If the previous customer was pumping regular fuel, I assume the refueling hose is still full of regular fuel, perhaps a couple of gallons. This would mean I'm initially getting a mix instead of pure premium fuel. Is this a genuine concern, or does the system have a mechanism for evacuating the gas pump hose between uses?
A: It is a genuine concern, but one that motorcyclists tend to appreciate more than car drivers. According to the American Petroleum Institute the gas-pump hose typically retains about one third of a gallon of fuel. So when you pump a couple gallons of 93-octane premium after the previous customer pumped 87-octane regular, your fuel load would be diluted (not to mention overpriced).
This is more important to motorcyclists because bikes have smaller fuel tanks and a lower tolerance for low-octane gas compared with most cars. I have found that high-performance motorcycles designed to burn premium fuel run poorly on regular. They generally do not have the complex engine-control systems that allow cars to run on fuels of varying octane ratings.
I don't think diluting your premium fuel with a little regular will harm your motorcycle, especially if you always select the highest octane rating available.
However, next time you're filling up you may want to get in line behind the driver with the highest-performance car in the station.