Solo in June 2010
I did the trip you fellows are speaking about in June last year on a 2007 R1200GSA. Ran Heindau tires, but I ran them from Calgary, across Labrador & NFLD and got fresh ones in Halifax, NS. You could make this trip on Tourances or Ankees, but if it gets wet or if the "rough patch" hasn't improved, you'll be clenching your sphincter the whole way.
In terms of "how far in a day," I road from about 1 hour north of Baie Comeau to Churchill Falls in one day. Biggest challenge was multi-mile dust plumes from b-train gravel trucks. Full sensory deprivation.
HVGB to Port Hope Simpson is a full 400KM, including something the locals were calling the "rough patch," 50kms of gnarly, muddy, rock-strewn goo. You'll need enough fuel for a full 400kms, plus some extra in case the rough patch bites you.
I stayed at Red Bay, about 45 minutes east from Blanc Sabon. It is where the gravel turns back to pavement. They have refurbished a wee building into thee nicely appointed hotel rooms with a beautiful view of the bay. Good restaurant, low key and bloody picturesque with an unobstructed view out to iceberg alley.
Camping is no problem, especially if you wish to camp between cities.
Early June was my timing, which meant no bugs & no black flies. You'll need some severe frosts to kill those things, so later August is likely the next best bet. Otherwise DEET bug juice and head nets.
It is a very cool trip. There is nothing terribly technical, but keep an eye on your mirrors. The truckers and locals drive fast (110 - 140kph). I'm no superstar rider and my speeds varied depending on conditions from about 50kph to 140kph. I expect I averaged something like 80 to 90kph.
Other nuggets; Yes, the north shore of the St. Lawrence is way better riding. It can get cold and wet - heated vest and proper sleeping bag & tent are critical items; Gross Morne is a jewel; Never drive past a gas station - ever. Carry extra water & some powerbars or something like that, it's 300 to 400kms between towns; Carry a tire repair kit as some of the road can be very sharp. Always be kind, polite and considerate to the locals, because it is the right thing to do and because they can help you.
I rode across the entire country last year: My favorite bits were Quebec City, Labrador, NFLD and the Cape Bretton Highlands (Meat Cove).
Best of luck. Keep the shiny side up!