Repairs Can anyone identify this part?

[Keats]

I just took mower apart, replaced the magneto (Brand new Briggs & Stratton magneto, it had a chip outta the black laquer on the outside, hope it doens't make a difference.) Also removed gas tank and cleaned etc. - put on new diaphram. So I am all done and trying to start it - it will come on and go off right away. Then I look down and this piece is on the mower. This is it:
lawnmower part - YouTube

Can anyone identify it? Sorry to sound dumb but I am unemployed and can't afford to hire anyone to fix the mower.

 

[Rivets]

That is a baffle which goes on the engine, on the same side as the carb. The end with the spacer goes behind the gas tank screw, which goes through it. The other end gets bolted under the shroud (cover) through the side bolt which holds the shroud on.