The firing order of a Honda motorcycle engine can vary depending on the specific model and engine configuration. However, one common firing order used in Honda motorcycles with inline four-cylinder engines is 1-3-4-2. This means that the cylinders are fired in the following sequence: cylinder 1, cylinder 3, cylinder 4, and then cylinder 2. It's important to note that this firing order may not apply to all Honda motorcycle engines, so it's always recommended to consult the owner's manual or service documentation for the specific model you are referring to.