Yes, the cylinder swap must be done by a service center. it requires cutting the top end seal. Do not buy any engine that does not have a lettered cylinder already They will not be legal and you will have to replace it at a potentially very high cost. A good rotax cylinder can cost well over $1000. I have seen them sell for $3000 to $5000. That is for a cylinder only. I do have a very good engine that I have been on the fence about selling. If you have not purchased one yet contact Christian Fox. He and I talk a lot about our engines and tuning so he can vouch for me.