It could be a little lean.

You have to remember what causes you to change a mixture setting. Are you running the same fuel as the folks at YS Parts and Service? I think they use both Cool Power and PowerMaster fuels on the service engines. Not sure about that though. Different fuels make a difference. The next major factor is Gardnerville/Minden Nevada is 6000ft of elevator. This will require the setting to be a little leaner than you in Dallas.

For reference the engine came with a double jam nut.......all 4 stroke engines should use a double jam nut on the prop. It could have backfired as it was getting low on fuel and got an air bubble in it too. This is always an option.

In the mean time here are some instructions on proper setup of the mixture setting on the YS engines.

http://www.probuild-uk.co.uk/factsheets/ys_engines.php

he has very good advice on setting it up.

For safety reasons you should have some way to hold the model when starting it up and flying by yourself.

Troy Newman
Team YS Performance