Originally Posted by Southgate Jonny
Hi Nevada. I broke my new engine in running opti 2 @ 80:1 from the get-go for half a tankful (approx. 1/4 gallon) then went directly to a 100:1 mix. Over 200 miles on this mix my plug is a perfect golden-brown and the engine runs surprisingly cool. I suggest raising the c clip position on your carb needle (and possibly going with a smaller jet size) because running lesser amounts of oil per gas ratio makes the mixture richer (more gas in a given gallon).
Ditto: Jonny is right on with this advice but you need to be careful and not go too lean. That is one problem running the 100:1 ratio. To get things right you really need to lean out the fuel/air mix because of the more fuel, less oil condition you are now giving your engine. Just don't over do it. A lean burn can shorten the life of any engine.
Your altitude above sea level will also play into the proper mixture of air and fuel.