An assembly and a method for maintaining and inspecting a wellbore are described. The assembly includes a body. Multiple magnetic wheel sub-assemblies are adjustably coupled to the body. The magnetic wheel sub-assemblies position the body within the wellbore and reposition relative to the body in response to a wellbore narrowing or a wellbore widening. The assembly includes a tool connection coupled to the body. The tool connection couples a well tool to the body. The assembly includes a control sub-assembly to control the magnetic wheel sub-assemblies and operate the well tool within the wellbore. The assembly includes a power sub-assembly to supply power to the control sub-assembly and the well tool. The assembly includes a backup retrieval mechanism coupled to the body. The backup retrieval mechanism couples to a retrieval tool.