User Review: Coleman Exponent Apex II
Price Paid: $20-40 used
This is clearly a highly functional 2 piece backpacking stove. I currently own 5 and use them for teaching backpacking stove/cooking skills. I also own several different liquid fuel stoves ranging from the old Optimus 96, 8R, 123R, Coleman 400, 442, 445, 450, 533, 550, Fyrestorm TI as well as the MSR Whisperlite and dragonfly. I have used many other liquid fuel stoves over the years.
1) Priming: Coleman uses a fuel line snorkel (the L-bend in the plastic tube on the pump) to mix pressured air from the top of the tank with the liquid fuel when the burner is cold. This helps to reduce flooding, but drains the pressure in the tank quite quickly on lighting, requiring addition pumping during priming. This is why they tell you not to fill the tank past 2/3 full and to pump it up good. The stove needs a good volume of pressurized air in the tank to prime properly. (I usually shake the tank vigorously after I pump it up to mix as much fuel vapor with the air in the tank before I light the stove)
With the kero gen tube installed, you need to preheat the stove with priming paste or alcohol before you open the fuel valve, this makes the pumping issue goes away. I prefer the Optimus and MSR priming method better (prefill the priming bowl with fuel, light, wait for everything to get hot then turn the fuel on). More often than not I will bring a small squeeze bottle (1-2oz) of alcohol or white gas just to manually prime the stove so I don't have pump the stove as much. A small amount of prime 1/8-1/4oz is all it takes to preheat the stove.
2) Simmering: Like most all liquid fuel stoves with a second 'fine control' fuel valve this stove does simmer quite well. It will also 'hold prime' even at very low simmer settings, not all liquid fuel stoves will. The burner design shields the wind and reflect the heat back to the gen tube. This is a great feature if you are truly cooking your meals not just boiling water. If you stay with 2qt pots and smaller the control valve doesn't get too hot to use.
3) Tank to Stove Fuel line: I don't like the design where the disconnect (fuel line connection) is at the burner. The MSR stoves and the later Colemans (Apollo/ Gemini/ Denali/ Fyrestorm) all disconnect at the pump. I have never had issues with my fuel lines and I have used the stoves several dozens of times over many years. The fuel line design is likely why Coleman discontinued the 450/445 Apex I/II stoves.
4) Stability: I prefer the Apex to the Wisperlite as it is lower and more stable. Especially the versions with the flip out 'lunar lander' legs.
5) Pumps/Repair: I always bring a spare generator (vaporizor) tube and a second pump assembly. Never needed them, but it is not a bad idea to pack these spares. I would rather swap pumps vs perform field service (there are a lot of little bits and pieces (including springs) to get lost).
6) Closing: Nice functional stove, nothing is perfect but these are good stoves. Other than the pumping and priming (a workout which I avoid by manual priming) properly maintained (keep an eye out for leaks) and operated they serve their designed purpose well.