I raced this year at the Canadian Nationals in Masters L0206 and finished 3rd. The engine I used was brand new with one day of break in on it. I set my carb float level, pin height air screw. I set the valve lash just before qualifying. Engine ran great. For me most of my time was in the clutch. I used the Hilliard Flame which from the chart engaged around 2900 rpm. I ran the briggs oil at 16 oz.
For out of the box, you cant get better then that. Nationals was such a blast.
That weekend though I never worked so hard getting the chassis to be free. The Vega Blue are super sticky and if your kart is bound up you will never be fast.
The engines are more expensive in Canada and with the dollar, but this is the best class to get into. Our fall club race this year we had 28 guys and it was a blast.