Old Briggs 5 hp on Rototiller

I have an old Bolens Rototiller with a 5 hp Briggs engine.

It has been just stopping during use and would restart easily.
Yesterday I filled the tank with gas and started it.
Gas began spurting out of the gas cap!!!!!!!!
So, I took out about 1/2 of the gas and restarted it.
Seemed to run ok, so I started to 'till the garden.
It stopped a couple of times and restarted.
Then, I was not able to start it.

Any ideas where to start looking to correct this problem???

Thanks for your time to reply.

Old Briggs 5 hp on Rototiller