Modern Vespa

Everyone:

this forum has been hugely helpful in the past, so I am hoping for good news. I have a vespa et2 kitted with malossi variator and 70cc kit. It usually goes 50+ mph. recently I had it serviced and now it goes 40, but I lose almost all power when I push the throttle past the 3/4 mark. I think it is the jetting. It was rejetted when it was serviced. HOWEVER, I rode it 20 miles after I had it serviced with no problem. I then filled the tank and added two cap fulls of 2 cycle to "richen it up" as suggested by the mechanic. That is when the dying at 3/4 open throttle started. Could this be the problem? (as I type this I am starting to feel like the answer is fairly obvious )

All ideas are welcomed

The mechanic is mistaken. Adding premix oil doesn't richen the mixture. 2T oil has nothing to do with mixture except in-so-far as it can LEAN the mixture out when premixed by displacing the amount of gasoline which travels through the jets at a given instant.

There is some debate, I have to admit, as to how bad this effect can be.

It is a common confusion to mix up "oil per volume of gas" ratio with the combustion mixture (which is fuel to air ratio). You do not want to run lean with your fuel/air mixture, especially on a 2T, and adding oil to the gas on a bike with autolube is a way to do this on top of fouling plugs with too much dirty grimy oil.

What things did they do to the scooter during the service?

If I were you, I would figure out what jets they put in, and I would drain the current tank of gasoline and run only pure gas in the tank. Do a plug chop (http://www.incriminators.com/plugchop.html) to determine whether you are running lean or rich. In this case, it sounds like you might be starving fuel at WOT due to the premix oil leaning out your mixture or too small a main jet. But it is hard to know for certain without testing.

I believe motorsport scooters recommends an 80 or 82 main jet for a 70cc kit alone (do you have a performance exhaust? If you do it should be higher than that)