Quote:
Originally Posted by
retryrider
Even on older bikers I thought it was same tank just with a two different outputs. One part way up the tank the other at the bottom and that's why you risked getting gunk in your engine if you used reserve.
|
That's right - with a carbed bike (and fuel tap), typically the 'on' position draws from the top of a tube, and the 'reserve' position from nearer the bottom - any 'gunk' is nothing to do with the level of fuel or 'old' fuel, only debris that might be sitting at the bottom of the tank itself (due to gravity), such as rust from a traditional metal tank... To be fair, all fuel taps [should] have a gauze filter as part of the tube, so its unlikely anything would pass into the fuel line - but its worth fitting an inline fuel filter on an older bike, just incase there is residue rust in there for example.
On an EFi bike, there is an electric fuel pump typically sited at the base/lowest point of the tank, which has it's own filter in... the 'reserve' light comes on when a float (typically at the top of the pump) is activated, once the fuel level drops below that point.
However, to answer Steve's original question - fundamentally the fuel is all in the same tank on any bike (unless you have an auxiliary tank on a rally bike for example), so every time you fill up, the new fuel mixes with the older fuel still left in the tank...
Jx