Welcome to the site !!
All of this depends on the year of the X (you did not mention the year , you just said New , but i don't know if that means New to You , or Brand New , did you buy it New or Used ??) , and elevation your riding , and if any mods are done to the bike
It sounds like it could be a couple things , it's possible it could be a worn Needle and/or a worn Needle Jet , the Needle jet is the main brass tube that the Needle runs thru and the Main Jet screws into , when the engine idles , and the Needle and/or Needle Jet are worn , it will give symptoms your describing as the Needle Jet is softer than the Needle so it ovals out from the vibration of the needle , its not noticeable to the eye , but you will usually find wear marks thru the Anodizing on the needle as a indication , or if you lower the needle (making the mixture leaner , but also shoving the needle taper farther into the needle jet allow it to move less , which should reduce the issue , though this should be only done for testing , as you do not want to lean the mixture any farther than it is from the factory , you will want it richer), as a result the Needle bounces around in the worn Needle Jet and you will get a rich/lean condition at idle and lower RPM's , , the other possibility is that the mixture is too lean for the location/elevation your riding at , where adjusting the Fuel Screw is needed , as well as a likely Pilot and/or Main Jet replacement to a larger size , the size of the jets , is determined by elevation , and temperature changes , and what your fuel screw is set at , your best bet is to remove the carb , so you can drill out the blocking cover for the fuel screw , so you can adjust it , and better yet , replace the awkward screw with a R&D Flex Jet
Another possible cause could be the Floating Valve Seal , which is the removable flat plate that attaches to the carb slide , if that seal becomes damaged or worn , it can give those symptoms as well
If you need more detailed info , go to the Jetting part of the forum and ask
leardriver , he is the resident jetting expert here , and might be able to guide you better than i can ...........Hope that helps some
Floating Valve Seal:
https://www.crfsonly.com/catalog/produc ... ts_id/3687
R&D Flex Jet:
https://www.crfsonly.com/catalog/produc ... ts_id/2792
Needle Jet and Needle:(Part # 27 and #38)
http://fiche.worldofpowersports.com/yel ... CARBURETOR