You can do that method or you can just put the thing on the ground and play with it . Either way you will get heat into the engine.
Sounds to me you have a high idle and a low fuel pressure.
Check all your pressure lines and fuel cap for leaks, check that the pressure nozzle on your pipe is not blocked with tig dags ,
Whats happening is you have a high idle to keep the engine running when rich, when you release the throttle to neutral there is a lack of pressure to return fuel flow. I would firstly lean HSN 1/4 turn , Lower the idle 2/8 , and then see what it does.
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