Shit thats lucky.
I saw the same thing earlier this year at the Hawkes Bay champs.
A guy on a SXF250 was going up the main straight hill when his packing came loose in the muffler blocking it.
It was just before the top of a 60ft jump.
It was like he put the brakes on. He was running second and one of the chasing pack nearly hit him as he went over the jump.
The hole crowed nearly shat them selves.