If you have a Walbro carb that requires opening over 1-3/4 to 2 turns on either needle to get the engine started you have either a bad carb or other issues in play. I have yet to see a Walbro carb that fits engines up to 150-170cc that would not start an engine with both needles at 1-1/2 turns open. Would the engine run good enough to fly? Almost never with any size engine but the idea is to get an engine started and then tune accordingly.

In reply to another post, if your engine is running fine, is not over heating, provides the power you need, and has good throttle response, why would you let someone mess with it?

No two engines are the same, just are no two carbs the same. Follow that up with propellers. Slight variations will always be present, which requires differences in needle positions from one user to the next. This does not include weather and elevation deltas which impact tuning further. That is why any engine tuning guideline that places hard limits/turn values on what to do will be wrong. Some engines will have a burbal no matter what an owner does. That is generally attributed to design issues.

The process can be easy or difficult, and what it will be is up to the user. If you are one that gets hung up on a number you will have a very hard time of tuning an engine.