Bike goes up in flames.

Motorcycling
1

http://www.newsshopper.co.uk/news/10370827.West_Wickham_man_rescues_biker_as_his_motorbike_sets_on_fire_in_Beckenham_road/

2

Lucky fella, well done the eagle eyed cager.

3

Would sparks by the engine be enough to cause a fire? (Genuinely asking)

4

honda “fire blade”

5

Probably an electrical fault causing arcing which the motorist saw. I have seen an arcing generator wire melt through coolant hose = impressive cloud of steam. Fortunately there were no fuel lines involved in that case.