I've never had much luck with the pinch test either but I found the one golden rule with GO motors is manually set the idle gap to .7-1mm before you start..remove the carb insert and use a drill bit to set it..I have some old imperial bit i found that happens to be .8mm..perfect..if the motor won't idle with this idle gap your mixture is WRONG somewhere..HSN flush and LSN flush or maybe 1/2 a turn in is where I've always got the initial idle stable..I started with a gen 4 7 port then a gen 4 3 port then gen 5 and 5.5 7 ports and now the MG66 and I set them all the same..set idle gap..start the motor ..if it chokes up a lot and won't idle unless you keep blipping it then lean the LSN a bit BUT DON'T TOUCH THE IDLE SCREW!! then I sling it on the ground and run very gentle figure 8's till I've most of a tank through it.you need to heat the chassis plate as well as the motor..to get a reliable tune EVERYTHING needs to be up to temp..then LSN for a nice crisp takeoff with plenty of smoke but not a huge cloud as it struggles to clear out excess fuel..NOTE!! if you have been idling for maybe 30 seconds the engine WILL load up a little and probably struggle to clear the unburnt fuel for a second or so..this is normal and doesn't necessarily mean the LSN is too rich.blip the throttle to clear out the motor then idle for 10-15 seconds max before trying a clean takeoff test..I can't speak for the GX motors but the 5.5 carbs are pretty sensitive..you only need to adjust maybe 1/8 of a turn at a time..SO USE A LIGHT HAND .hehe..then do a few good high speed runs and maybe tweak the HSN in a little..again bear in mind that as you lean the top end you are also leaning the bottom so you might need to revisit the LSN and richen it a fraction.Personally I always leave the LSN a touch rich at first and then it usually falls perfect when I tweak the HSN..