Pros: Killer BTUs, Reliable, Functional, and Durable.
Cons: Heavy and Bulky; Replacement Generator Too Costly.
If the Coleman made one stove that will be remembered in history, it would be the green suitcase stove. Unlike smaller stoves Coleman makes, the green suitcases rarely give any trouble. I bought my 425F in 1980, and it served faithfully until 2003, when it began to sputter. I thought it was time I had to accept the fact that my 425F had lived its natural life. By the time I discovered its cause and fixed it (it was the generator that was clogged up with carbon), I already had bought a barely used 424 Dual Fuel, an improved version of 425F. I just could not give up on a faithful servant that served me for 23 years, just because it became old and decrepit, as those corporate CEO types do with their employees.
425F comes with one small and one large burner (the more recent 424 has equal-sized burners). The large one, when used alone, produces a fairly impressive blue fireball (rated at 11,000 BTUs). If used with a large diameter pot or pan, the overflowing flame will scorch the front portion of the wall, where the fuel tank is installed.
Because of the smaller output, the small burner is good for simmering. If you are cooking two different meals at once (you will, if you are with a large group), it is convenient to rotate the pots for simmering, while the other is boiling away. But because of its smaller output, it is no good for boiling: takes too long.
The fuel tank is more than adequate for a weekend trip. I never found out how long a tank full of fuel lasts, because it lasts too long. I just forget to count the hours of operation. Take my word for it: it will last a few days, cooking for a large group. I guesstimate it would last three hours easily at full blast. Its fuel efficiency is excellent, even with such a large burner.
A funnel is a must for all stoves, for safety and prevention of spillage. I prefer the ones that come with a built-in filter. After long years of service, which your 425F will undoubtedly give, things tend to collect inside the fuel tank, and they will clog up the fuel delivery eventually.
The most common problem one would encounter after 10 or 20 years of service is the dried or worn-out leather pump cup, or the clogged generator tube. Coleman must repent for charging so much for a replacement generator. One does not really need to change the generator on 425F often, but when one has to, its price will outstrip whatever cash value is left in the 20+ years old stove.
So invest in a propane gas blowtorch instead: you can get one for the same price of a generator. When the generator is suspected of being clogged up with carbon deposit, remove the generator from the fuel tank, and blowtorch that thang! Any carbon-based deposit will be burned off. Brush the coil inside with a brass brush. Sandpaper the needle with 220-grit sandpaper or very fine grade steel wool. Replace the tube and you are back in business. Now you have a free blowtorch. Ha!
Other items, such as pump-related parts, are readily available in a kit form. Compared to the generator, its price is acceptable. If your stove is an old model that came with a leather pump cup, you can actually oil it up to restore the flexibility. Or, you can cut out a piece from an old backpack or a discarded handbag, saturate it with oil, and add it in front of the less-functional cup. The new one will augment the airlock and will pump up as good as new.
Sometimes combustion takes place inside the expansion chamber into which the generator tip is inserted. When this happens, you will hear a loud piping noise, and the flame will not come out of the burner in a normal fashion. Just remove the generator tube by pulling the fuel tank off the stove. Wait for it to cool, and relight.
The stove comes with the clear instruction inside the cover panel. Follow it, and the stove will light up easily. Fill the fuel tank up to the bottom lip of the tube inside. Make sure the fuel cap is closed finger-tight. Check the valve for the small burner on the left side of the stove is tightly closed. Check also the main valve wheel is closed all the way. Pump up until you feel resistance. Flip the little brass lever up. Light a match and place it next to the main burner. Keeping your head as far away as possible from the burner, turn the wheel to open the fuel valve. When you see the blue needle-like flames remain steady on the burner, flip the lever down and pump up a few times until you feel the resistance. Turn the piston clockwise to close it.
A word of advice: after lighting, do exercise patience and let the flame burn up a little while, before turning the brass lever down. If you flip the lever down too early, the generator is not hot enough to vaporize the liquid fuel: an orange, sooty flame will shoot up. Then you will need to wait even longer now for the burner to cool down, before you can try it again.
425F has a nice, heavy-duty grill that will support heavy pots with no concern. It has a pair of flip-out windscreens that function well in the windy weather. If you plan to keep its paint job intact, wipe any spilled grease off the stove after each use. After about 15-20 years, I discovered that the oil-spattered portion of the paint became loose, and came off, when I decided to clean it up.
Unless you let your Sherpas carry all the gear, you won't want to take 425F on mountain climbing or hiking. 425F is excellent for car camping. It handles a large group like a breeze. It is also a very good backup stove in case of the power failure. With a Coleman's folding oven, pastries and loaves of bread will delight your camping palate with the luxury of home-baked quality.