Hey Jaffa if they got fuel on top of the carby/tank then all that is needed is an ignition source, only one that comes to mind, is when you put the controller to stop you get arcing at the stop contact, which is around that area. (but who knows what they were doing)

Here is a burnt out Victa I rebuilt, the back was choked full of grass and more than likely soaked with fuel.
It was extinguished with a powder extinguisher. Owner wont tell you what really happen, probably embarrassed.

[Linked Image]
[Linked Image]


Happy is he who penetrates the mystery of things.