let it cool, and then loosen the glow plug to let atmospheric pressure in. The cooling will condense the air in the combustion chamber and create suction. Tighten the plug again, then heat the head and the top of the case to 200 degrees fahrenheit. If it is cool outside, the piston should push itself back down, around this temp. This is due to the expansion of the air after reheating. You should preheat your head and case to 200 degrees before attempting to turn it over.

I did this procedure with a GX-5R on sunday and put over half a liter (800cc) of fuel through it before setting it on the ground. Engine was kept at 210-230 degrees for the entire period on the box, and total fuel consumption was measured with a fuel gun. I did this for 2 tanks (250cc). This was followed with another 800cc of fuel on track, without pushing the RPMs down the straights. Temp didnt exceed 250, and was spot on around 230. Fuel used was a fresh gallon of 30% of a premium branded fuel.