Mill Supply carries replacement Mufflers that fit Clinton Lawn Mowers as well as other Lawn Mower Parts.

Muffler fits, 2-1/2 to 3-1/2 hp. Fits models N, 5S, 6B-F, 6-R, 6B-HS, 6B-H, 6, 6R, 6F, 6S, 6B-S, 8, 8F, 8R, 8P, 8B-F, 8B-R, 8B-H, 60100 (2 hp horizontal): 80299, 80300, 81997, (3 hp horizontal). 4-3/4" length, 1/2" plated pipe.
Mower-parts.net carries replacement parts that fit Clinton Lawn Mowers which most often need to be replaced such as Clinton Mufflers and other Lawn Mower Parts.