Usually when a two stroke aero-motor is surging, it is too lean. Smoke from
the exhaust is not always the best indicator of the fuel/mixture setting. You can
have smoke from the build up of oil in the muffler. You can also have smoke from
a lean condition, causing extra heat in the muffler, burning that build up of oil.....
and fooling you with the look of richness.

For all practical purposes, a good smoke trail is the perfect sign of a happy engine.
Make no mistake about that....smoke comes from the oil burning, not the methanol.

Generally, if a two cycle aero-motor is surging....you should open the high-speed
needle at least 1/4 turn to get it back into the ball park. Some engines lean out
so much in flight, that the initial carb setting necessary for a perfect flight seems irrational....especially to the owner of the plane who has the problems.

As an example.....A Guy had a Sig Wonder with some little .15 in it. The thing would
go about three laps, then die out. I reset the high speed needle with 12 clicks out
for the proper setting....that's darn near a full turn out.

Some engines when set for peak will run for about 10/15 seconds....then lean out.
You have to open the needle 3-4 clicks. Then it does the same thing....peaks out,
runs strong....then wants more fuel.

There are of course....several things that are adding to the equation. The bottom
line is....you have to wait each time you change the carb mixture setting to find
out what the final result will be. If the carb isn't set right....you will know about it
very shortly.

FBD.