Richen the mixture (screw out) 1/4 turn at a time, definitely lean IMO. @SlammedRanger helped me with my carb issues and he was absolutely spot on!
Similar procedure except hold the gear lever up until you’ve come to a stop, holding the lever up (or down) will keep clutches engagedYou may need to talk to some of the utility quad guys on here on how to properly do the test. I do it on sport quads with a clutch. And when i hit 4th gear and wind it out to just before rev limit i pull the clutch while flipping the kill switch and roll to a stop. Thats the proper way to do the test. I havent the slightest clue how to do that on a quad with no clutch lol. But you will want to warm the quad up on your current plug. Then slap in a new one and go real hard on the throttle through the whole test.