Why do you do that? I don't think it is good for your bike.
I see opinions go both ways. I think it is a good thing. Letting it run will keep all the engine components and gaskets lubricated, eliminates condensation buildup, ensures fuel lines will not gum up, and recharges the battery. I let it run long enough that the condensation in the pipes is gone and it is running smooth.
I don t think it is good to start it unless your going to let it get up to temperature to drive out any condensation and let the hot oil get distributed throughout the engine.
Why do you think it is not good for a bike ?