Heard this scenario many times and sorry to say they are right 75% of the time. Today's carb are built to run so lean, that it does not take much to cause problems. I don't like the idea that the dealer is not opening up the carb before giving his diagnosis, but I suspect he is giving you the worst case scenario to prepare you. Today's engine manufactures are making it very difficult to warranty carb/fuel related problems, which means the customer is paying. I would start by asking the following questions.
1. What will it cost to clean and rebuild the carb?
2. What is the cost of a new carb?
3. Will this repair be covered under warranty?
4. What is the difference in the length of time it will take to rebuild or just replace the carb?
5. Will the dealer contact the manufacturer to help you cover the costs if not warranty?
6. What will be done for $225?
If the dealer acts defensive, get out of there and go to a different shop. If you feel comfortable with the answers you receive have the dealer do the repairs, but remember you may have to pay $225, which seems high to me, but I'm not there. You are going to have it repaired, so make sure it is done by someone you feel comfortable with. Because it is an engine, most good dealers can do warranty work for you. We do a lot of work on units which were sold by two other dealers who sharply undercut the costs of their whole units to get them out the door, but they have service departments who throw parts at problems, charge for repairs that are not needed and have a labor rate 15% higher than we do.