Hi Energyman,
My answer to your query is the standard, "No, but a friend did".
He had a couple home steam cleaners. The first was designed to take the wrinkles out of suits and it did nothing for cleaning the bike.
The second one was built more along the lines of a tea kettle with an extended spout from which steam emerged. It was surely effective, but at some cost. It did alright on metal components like the chainrings and deraillleurs, but I was assigned the task of mopping up the greasy drippings. I think it is fair to say the steamer doesn't "clean" a bicycle so much as it ehm, "displaces" the dirt, grease, and assorted debris such as leaf mold, manure and dead worms kicked up from rainy-day rides. Some of those things sort of reanimate or at least inflate when exposed to steam. Ew, says Towel-Man Dan. Some things are best left be.
Things went considerably less well when he turned his attention to cleaning the tires. The steamer did a great job, but a little less than a week passed before the sidewalls developed a crazed surface and then large surface cracks. We both concluded the steam must've cooked 'em, though it didn't feel that hot at the time.
I can tell you, without hesitation, this is an Extremely Bad Activity to pursue on your newly-installed light-colored carpet and will not ensure domestic tranquility in the hours that follow. Just sayin'. I left after as the discussion escalated from shock-and-denial to something louder.
So, overall, this may fall into the category of "Great Idea! Try It On Your Bike First And Lemme Know How It Turns Out" rather then "Great, I'll Do It To Mine Saturday".
Hope this helps,
Dan.
