Sounds like the baffle has come out of the exhaust as they shouldn't be that noisy.Yes a little more than a modem mower but still shouldn't be that bad.
I think for memory that one should have had these taps.
[Linked Image]
These two are currently on eBay
Fuel Taps
As the round plastic ones certainly were not around when this old girl came out.

Here for a good time,not a long time.