The study we mentioned twice before is now online. Reading through the findings confirms a few things, the study reflects the Swiss traffic fleet and the vehicles in use there. It includes two stroke motorcycles or scooters in the mix which we do not have in the U.S. and the motorcycles, as outlined previously, were not new, in fact some were a decade old.
Other than confirming the fact older motorcycles, especially two strokes, emit more of some types of pollutants than the average car, I'm not sure what it really says. Unless you are going to ban or force backward modifications to existing motorcycles, what have you proved?
If you wish to test motorcycle emissions, check the motorcycles and scooters currently on sale to give an idea of the current state of the technology. Any conclusions or recommendations should be based on current, not historical, data. It may very well be that current emissions, when taking into account actual miles ridden and the number of motorcycles on the road, show you have essentially no "emissions problem" at all.