Yes, there are checkpoints. Make sure you hit those. But I think your problem might be not going wide enough around the rock. Anyone would naturally fear falling into the lava, so they'll tend to go inside at first. Make sure you adjust if you have been doing that.
Guys, I can't even make it up to the rock that way. I've done it randomly sometimes, but when I actually try to, it doesn't work. Can anyone FULLY actually help me, like a vid of the spot where you need to do a wheelie, hop or w.e?