As long as you can keep moving at a reasonable speed your radiator can be just about empty and you will not overheat the engine.

I smashed open my radiator whilst green laning on a fairly warm day and managed to ride 30 miles to home at low revs on open roads without any increase in normal working temperature. However, I managed to choose a route where I knew I would not be stopped for anything more than half a minute max.

I would not expect this to work well in stop-start traffic. Switching off the bike is only likely to further increase temperatures as water will not be moving.

I would highly recommend for any long trip that you take a bottle of hyperweld or similar. I have permanently repaired 1 Peg radiator and 2 car blowing head gaskets with this. Details under blown head gasket (ADD LINK)