I did it 14 years ago on my '02 Vee. Great trip, and may do it again someday.
I think there is another gas stop available now that wasn't back then. At that time the first stretch of James Bay Rd was 381km with no services/fuel. We carried extra. Heading up, we took it easy trying to maximize fuel, and only the Harley in our group ran out.
Be prepared for cold weather riding. We traveled there in mid August and one morning was 6 C. Also go prepared for blackflies. Never have seen as many at one time.
We took 5 days, but stayed in hotels/motels. Have to make reservations in Radisson well in advance if you plan to stay in the hotel there . We did 2 days to Radisson, then an easier day in the middle to go out to Chisasibi on James Bay coast. No point in going that far and not going to James Bay
The trip to Chisasibi in my opinion was the highlight, and not to be missed. Fantastic road with beautiful sweeping curves best experienced at 150-160 kph, or so I'm told
Then there is a short stretch of gravel to get to the actual coast.
The 4 of us also had a personal tour of the hydro dams/installations, so our middle day was more relaxed and did only about 260km.
Another 2 days home. On the James Bay Rd portion, no traffic, no police, and fairly good road made for a very quick pace
and even I ran out of fuel just short of the service centre.
In 5 days we covered about 3850km from Toronto and stayed off major highways whenever possible.