Hi Wheelybin, welcome to Outdoorking.

There are two main potential causes of a shutdown after a few minutes of running. The first is a temperature sensitive ignition module failure. The second is a moving blockage in the fuel line or float bowl, which passes fuel until it moves (with the fuel flow) into a blocking position - then drifts back out of blocking position when the fuel flow stops. In most cases, if it is an ignition failure, if you do a spark test immediately after it shuts itself down, it will probably not produce a spark. The standard way to check for a moving blockage is to disconnect the fuel line at the carburetor, place a cup under the hose, turn on the fuel, and see if it continues to run full-stream into the cup. If it does, remove the carburetor float bowl and see if there is crud in it.

We can talk about each of these tests in detail if you wish. Meanwhile, you might be interested in this thread:
https://www.outdoorking-forum.com.au/forum/u...mp;Words=gv400&Search=true#Post43287

In that case it took us way too long to get there, simply because it was a soft moving-mass in the fuel line, so it would pass every test except the sustained-rate-of-fuel-flow test.