Re: different way to change fuel/air mix?
Mixing diesel would not be a good idea either.
If you must change your mixture some other way than the correct way, change the amount of oil you use. A 24:1 mixture has half the gasoline that a 50:1 mixture does. (don't get crazy on me math freaks...).
Sooo, using that you can adfjust your fuel to air ratio quite a bit.
Other fine tuning of the mixtures can be done by adjusting the float level up or down, and the amount of back pressure and intake restriction can also be tweaked a bit.
Have fun, watch your plug for changes and don't run it too lean.