That’s right, need to check the carby and its fit, then follow the manual for mechanical balance, then ensure throttle travel is same for both; a visual assessment then run up to verify all good. Two of my experiences are July 2024 asked by neighbour to sort a very rough running Rotax ULS (history was that local lame shop had made adjustments) I adjusted carbs (first recording where settings were) after balance all good. The setting where all over the show, looked in aircraft log no record of the work or who did it. I found out from another source.
2nd example years before above and on a SavXL did M balance but roughness when rpm increased, a bit of further checking and head scratching found the throttle lever on the carb had been bent for clearance, only a little bit and pretty much impossible to see. Had to fit a straight edge (6” eng rule) to see the slight curve. When straightened all good. All part of learning and building experience.