I would stick with 16 to 1 using a good synthetic. When you reduce the amount of oil you richen the air fuel ratio. Here is a quote from Pete Muller a expert karting guy who did a lot of enduro racing.
"Yep... I've actually run up to 13oz per gallon of castor oil in a KT100 (a 10/1 ratio!) with excellent results.
Definitely: the more oil I ran, the more power the engine produced... up to the point where plug fouling became a nuisance.
I think you'll find these results unanimous among anyone that has systematically tested."
I realize it is not a racing engine but it applies to all. I run 16 to 1 in all my 2 stroke bikes and lawn equipment. I use moutil or redline oil in the racing engines and synthetic echo oil for weed wackers and blowers.
"Yep... I've actually run up to 13oz per gallon of castor oil in a KT100 (a 10/1 ratio!) with excellent results.
Definitely: the more oil I ran, the more power the engine produced... up to the point where plug fouling became a nuisance.
I think you'll find these results unanimous among anyone that has systematically tested."
I realize it is not a racing engine but it applies to all. I run 16 to 1 in all my 2 stroke bikes and lawn equipment. I use moutil or redline oil in the racing engines and synthetic echo oil for weed wackers and blowers.