Follow the hose from the fuel tank, it has to go to the carb at some point. It'll probably look a lot like the one on a lawnmower. Most of those are 2 strokers, so it will more than likely be bolted to the crankcase.

I really liked the way that guy fixed the one he stole from Sting at the end of Quadraphenia....

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python