There's always somewhere to buy gas, get food and to sleep. No part of Vietnam is uninhabited and everyone drives similar vehicles to what you have. Highly recommend you go north, it's incredibly beautiful.
Yeah, we're driving to Hanoi so we will make it to the north. I'm talking about a specific stretch of the road next to the Lao border that's basically uninhabited because of mountains and it's a national park too. People I met said they didn't see even another bike driving by for about 2h. It's not the kind of train you ride unprepared on a crap bike.
I'm pretty sure that the Highway and the trail you're talking about are the same thing, though there are 2 paths to the HCMH, east (Đông) and west (Tây). West is the more barren one, I rode it for a while, and it's not that bad. The East one is far less barren and still very pretty. In your other comment, you went from Nha Trang to Hoi An? I did the same but went through Pleiku. If you're in Hoi An, you've already gone past the barren part, and I still highly recommend you go the HCMH route after Hue, especially if you are going to Phong Nha-Ke. I think whoever told you that meant north of HCMC, not north in Vietnam.
Yeah, we'll probably stick to east - less barren is better as we have no riding buddies and no backup. We'll probably go west up to the national park to see then caves and then come back east. Thanks for all the tips, how come you know that part of the world so well?! When did you ride it?
Wait, what I'm saying you're already past the East/West HCMH thing, unless you're talking about HCMH (west) and 1A (east), if so, I can't recommend highly enough that you avoid the 1A, as the HCMH is pretty, not barren at all, and you can still get to villages where westerners are rare and the people are incredibly kind. I promise, you will not go without. I spent 6 months last year going from Beijing down the coast all the way to Myanmar, and I'm one of those overly-methodical researchers before I budge an inch. There's tons of mis/out-dated information on blogs and out of people's mouths, so I tried to synthesize it all so I could actually make sense of it at some point :D