The 5 most popular story-specific questions about Motorheads Season 1 Episode 9 'Ignition' are:

1. What is the significance of the flashbacks to 17 years ago involving Christian's fate and how do they connect to the present events?
2. Why does the engine fail to ignite when Cate tries to start the rebuilt car, and what does this imply for the characters?
3. What is the nature of the rivalry and stakes in the race between Zac and Ray at the speedway?
4. What is the devious plot involving Ray, Ezra, and Logan to steal Bruce's secret car collection, and how does it unfold?
5. How do the relationships and alliances between characters like Curtis, Brooke, Marcel, and Logan develop during this episode?

These questions focus on key story elements such as character backstory, conflicts, and plot developments specific to episode 9, as detailed in the episode summaries and reviews.