Yes if you had a small gas leak when the motor stopped it shouldn't be too difficult to have a shut off valve controlled by the spark.
If the gas was leaking a lot, a safety regulator would automatically turn the gas off .I have a few safety regulators as I see them thrown out with old BBQ s. The safety regulator Valve is good as it also tells you how much gas is left in the bottle.
When I looked on Gumtree in the morning I saw a 3 kw generator with a Briggs 8 hp selling for $75. but was in QLD.
I far as I know the cheap LPG converter isn't going to be suitable for 8 hp but the KN Garretson type converter will work well and has no problem shutting the gas off when the motor stops.
