How do you repack an ap 650 Spark Arrester?

Actually they are not meant to be packed, BUT You can, take off the large snap ring and pull out the canister and wrap it just like any other muffler you would pack.

Cut proper, Roll as tight as possible tape with masking or scotch tape to help put it back in, and it will help lower the db, sound, which is the only reason you wold want to do that with this particular Muffler. Answer Spark Arrestor Model AP-650