Two things you might want to know about that little write up...
The engine is preset for a certain amount of back-pressure, usually supplied from the muffler.
Add a high volume hose and large car muffler, and the back pressure will be lessened, and you can harm valves or pistons.
Scavenging will suck the fuel right out of the cylinder if there isn't the correct back pressure,
And that leads to Lean cylinder, over heating piston and valves, ect.
Your fuel efficiency will go down substantially...
Since there is no back pressure to keep the exhaust from scavenging the cylinder, you will loose raw fuel out the exhaust pipe and the cylinder won't produce as much power.
*IF* you rig up a secondary sound suppressor, clamp it to the ORIGINAL MUFFLER and don't just thread a pipe into the exhaust port or bolt an open pipe nipple on the engine!
Might be a little more difficult to do, but your engine will last a LOT longer if you do...
Another way to keep things more quiet is to not buy those lawn mower engine generators!
Get a larger generator that has a LOW RPM ENGINE with larger displacement (or two cylinders)...
Lower RPM's means you are using the same amount of fuel,
Two cylinders or larger displacement singe cylinder means the engine isn't as sensitive to back pressure changes, and there for easier to quite,
And with low RPM's you don't have nearly the frequency of firing noise...
I have two different Onan gensets, both 2 cylinders, both low RPM units,
(around 1,800 RPM compared to the 'Lawn Mower' engines that turn about 3,600 RPM)
And with the factory size 'Tractor Muffler' attached, you can stand by the exhaust and talk in a conversational volume with no problem.
I started out with the Lawnmower engine units, and they just simply drove me crazy! Couldn't take it, so I started looking into what they used in RV's and large Boats...
That would be Low RPM two or three cylinder units!