Here is the parts manual for that engine, see if you can ID, for us, the broken part
http://www.briggsandstratton.com/mai...=MS0295_LO.pdf
Look at page number 6.
Please remember that B&S builds the basic engines, sell them to mower makers they will add the extra things like tanks, to fit ever mower they making. If you can't find the part in the book, take a picture of the engine showing the broken part.
BG