too many possible scenarios ... in known margin fuel areas like certain parts of SA. it's common for mama fuel vendors to operate out of 55 gal drums.
it's not possible to drain every last bit of fuel out of 55 gal with a barrel pump. say one time tank held diesel, then filled with gasoline. a gallon or so of diesel mixed in with gas will cause major problems with a high compression engine.
make sure you've got a big honking battery. Lots of cranking figuring out what's wrong and/or getting things going again.
easy to fix ... drain fuel, then idle out remaining fuel... when engine no longer knocks under load ... good to go.
can very difficult to hear engine detonation. especially with helmet and/or ear plug on. but the common giveaway is lost of power.
bad fuel is not the only thing that causes loss of power. but if loss of power happens immediately after refueling. a load of bad fuel is suspect!
STOP .. don't ride it out ... take your helmet off, then listen for engine knocks. once someone knows what to look for .. a major trip ending problem is avoided. broken rings, broken pistons, etc. $$$$ ... NO knock sensor to retard timing, so operator has to be the safety.
sure hope this info gets passed on ...