These were a great motor. We found they didn't like the JP series of pipes all that much unfortunately.
If you can get your hands on a GO 2072 pipe I would recommend it. This will bring the GX Series motors to life and give you better run time as well.

Run them on 30% fuel with a medium plug. We found the O'Donnell 97T a great plug with these (Werks #6 plug would also work well).
Most of our running is at close to sea level - so plug choice may vary depending on where you live.

These motors run a long LSN in the carb normally - but I remember that a large percentage of the motors imported into the US were factory fitted with a short LSN at the request of the importer at the time.

If you do have a long LSN model (where the needle remains in the fuel delivery tube right up to WOT), then the tuning will be different to a normal short needle model.
For the long needle version the HSN is set only a few hours in from flush at best (it only effects the last 5% of the rev range). All tuning is then done on the LSN.
If the HSN is too lean, it will result in severe lean bog at or below half tank level. It's quite obvious when this situation exists. Just richen the HSN an hour at a time until the lean bog goes.
From memory the LSN sat at about 1/2 turn in at race tune - depending on fuel, plug, pipe, etc etc.

If you have the shorter needle version (which I suspect), set both needles to flush with an idle gap of around .5mm.
Tune in both needles from there until your were you want to be tune wise.

Hope that helps.