Translations:KAVAN AP09A - Instruction Manual/81/en

3. With the engine running at full throttle, carefully raise the nose of the model to an angle of about 60 degrees. The mixture shouldn‘t get too lean, but you should hear a slight increase in speed. This is normal. If the engine stalls or loses speed when the model is nose up, the mixture is too lean and the needle valve needs to be opened slightly. The engine must always emit a clear trail of gray smoke when running.