With the valve chest covers in place and the painted cylinder cladding fitted, it was a good opportunity for the chassis to be test run on air. To achieve this an air line was attached to the superheater and air was pumped via a bicycle pump. Plenty of oil was applied to all working parts. Any slight unevenness in running can normally be overcome by minute adjustments when the locomotive is running under it's own steam.
If all okay at this stage, the return cranks are drilled and pinned to ensure that they are held in place for when in service.
Roundhouse recommend that if the superheater hasn't yet been fitted, and therefore the chassis is untested, do not pin the return cranks in place, but wait until you can carry out a test run.