i say fuel or spark...

check plugs, check wires/coils with multimeter...if that all goes well then it's fuel...check injectors with multimeter...then fuel pump.

 

Took a stab at it 'eh Tahoe....or is that pin the tails on the donkey, til you get it right stab. Pick one man. We'll make a pool.

 

you know...check the air filter first.

you can pick one at a time or cluster bomb it...muhhahahha

 

Did it just start doing his or what? What kind of trouble diagnosis have you done, if any?

What do the sparkplugs look like?
Have you noticed an increase in fuel economy with no change in riding style? How about a decrease in economy?

 

i know when my bike was running on 3 plugs it wouldnt rev past 5,000rpm

 

so based on my calculations, he's running on 3.56 plugs right now ;-)