How do you know what needle to use?

[brentn]

This one has eluded me,

Finding the pilot is easy, it's in the sticky at the top of this forum. Finding your main isn't so bad either, WOT plug chops.

But how do you find out what needle to use, what clip to put it on? Are there any tell tale ways to find out what to use?

Thanks for your help

[2strokezuke]

Do the same as you would with WOT. run it in mid RPM, cut the engine without letting it rev down and check the plug. If it is running lean at the beginning of the transition stage and rich at the end, or vice versa, you need to change your needle. Otherwise, much more likely, you only needed to move the clip position to tune it right.