How many watts does the stove use? You should keep continuous load under 80% of max so 450-480 watts continuous. Try it out before you need it !
I looked up Harman Stoves, for a U.S. 120v model the start up current is 4.2 amps and running amps is 2.8 amps. That means that you need 576 watts to start and 336 watts continuous . Your start up is close to max but it should work.
Ran a 1/2" electric drill rated at 500 watts continuous for over an hour. Adjusted the generator voltage output to within Harman's specs of 130 VAC max at no load and 110 VAC min under load. No overheating or wild fluctuations in engine rpm. With a surge suppressor in line I think I'll be OK.
After monitoring the electrical output and setting your Genny RPMs, it is also valuable to monitor an appliance like a dehumidifier, freezer, coffe pot or TV for how much it is eating your disposable income. I own 3 of them and they have performed perfectly for 15+ years!
As CycleRob says the Kill a Watt is a good tool to have. I have a small 400 watt Onan generator. With the small engine the addition of different loads can vary the voltage quite a bit. You can use the kill a watt to adjust the Hz to 60 ( if this is a U.S. 120v ) for the average load your pulling. If there are any computer type electronics involved setting the Hz is probably more important than the actual voltage.
Grumps--Had to run my Harmon pellet stove with my EF600 and an inline surge suppressor. Ran it for 2+ hours---no problems whatsoever. The generator ran smoothly and showed no signs of lugging or overload. No damage to the stove's electronics panel, ether. I was initially concerned, but because the EF600 is an invertor everything ran very well.