Cutting a wellbore tubular

A method for cutting a wellbore tubular, comprising:

• running a downhole tool into a wellbore that extends from a terranean surface into one or more subterranean formations, the downhole tool comprising:
• a housing;
• a seal that at least partially circumscribes an external surface of the housing;
• a hydraulic motor assembly positioned in the housing and comprising a hydraulic rotor fluidly coupled to an opening in the housing and a shaft coupled to the hydraulic rotor;
• and
• a tubular cutting assembly coupled to the hydraulic motor assembly, the tubular cutting assembly comprising:
• a bearing coupled to the shaft, and
• at least one cutting blade coupled to the bearing;
• moving the downhole tool through the wellbore such that the housing is fluidly sealed against the wellbore tubular with the seal;
• circulating a flow of wellbore fluid through the wellbore tubular and to the hydraulic motor assembly through an opening in the housing;
• rotating, with the flow of wellbore fluid, the hydraulic rotor to rotate the shaft;
• responsive to rotating the shaft by the flow of the wellbore fluid through the hydraulic motor assembly, generating a centrifugal force or inertial force;
• extending, by the centrifugal force or inertial force, the at least one cutting blade from an external surface of the housing;
• and
• responsive to rotating the shaft by the flow of the wellbore fluid through the hydraulic motor assembly, cutting at least a portion of the wellbore tubular with the extended at least one cutting blade.