The Vmax 7 will overheat and "boil spit". If it over heats, its usually because its running to lean. Sometimes you cant tell it is overheating until you drop the throttle to about idle, it wont idle, it will die. just richen it up and it will be fine. The Vmax will run rich with plenty of power to fly the Heli. You dont want it to rich. You want to at least lean it out then back off about 1/8 to 1/4 turn. Or you can add a washer under the glowplug.
Ive noticed that some of the individual washers both for the Vmax6 and the Vmax7 are different thickness, they arent all the same. This seems to be more critical when adjusting the Vmax6 but not so much with the Vmax7. Tuning the V7 is a whole lot simpler. washer stack isnt as critical when wanting to get enough power to fly the heli. The power is there whether its running rich or running lean.