Also, when it goes back together, make sure you don’t mix up the left and right carb bowls. Make sure to use a new line for the choke tube between the carbs. And check that the cut away on the carb slides face the back of the quad. All simple stuff, but sometimes guys get in a hurry and over look it and chase issues because they were sure they did it right. Double check everything.
If the rest of the motor is stock including air box, 27.5 pilot and 280 mains should get you right in the ball park. If it’s got pod filters, maybe 290-300 mains.
Give it some fresh spark plugs, set the pick up gap on the flywheel, and see what it’ll do.