Why stoves fail quietly
A canister stove rarely dies in one dramatic moment. It loses pressure slowly. The jet picks up soot and fine grit from a season of dusty campsites, the O-ring between the canister and the valve hardens in the cold, and the burner head takes a knock in the bottom of a pack. By the time the flame turns orange at altitude, you have been carrying a stove that was already half broken for a month.
The good news is that almost all of it is serviceable. A blocked jet, a perished seal and a bent burner head are all fixable with a wire, a spare O-ring and a careful hand on the spanner.
Reading the flame
Before you take anything apart, light the stove and watch it for a full minute. A clean blue flame with a steady ring of small jets means the burner is fine and you can stop there. A yellow tip that flickers, or a flame that surges and drops, points to a partially blocked jet. A flame that starts blue and then goes yellow after thirty seconds is usually a fuel or canister temperature problem, not a dirty jet, and cleaning will not fix it.
Write down what you see. It is the fastest way to tell whether the service actually changed anything when you test it again.
Disassembly and cleaning
Work on a light-coloured cloth so small parts do not vanish. Remove the burner head, then the jet below it. Most jets unscrew with a small flat spanner, and the brass is soft, so hold the body steady and turn the spanner, not the stove. Clear the jet with a fine wire or a short blast of compressed air from the outside in. Do not push a needle through from the inside, since it can widen the opening and change the flame.
Inspect the O-ring where the valve meets the canister. If it is shiny, cracked or flattened, it is done. A replacement costs almost nothing and is the single most common cause of a stove that leaks or will not hold a steady flame.
Reassembly without overtightening
Brass fittings seal on the thread and the O-ring, not on brute force. Tighten the jet until it just stops, then a quarter turn more. If you feel the metal give, you have gone too far and the thread is now a slow leak. Test with a soapy water dab around the joints while the stove is lit, and watch for bubbles.
Storing it through a damp winter
Seals perish when they sit compressed for months. Before the stove goes into storage, back the valve off, wipe the body dry and leave the canister detached. Keep it in a cloth bag rather than a sealed plastic box, so any moisture that gets in can leave again. A stove stored this way will usually light on the first try next season.
Spares worth carrying
A spare O-ring, a spare jet and a small multi-tool cover almost every field failure. They weigh almost nothing and fit in the same pouch as the stove. If you only carry one spare, make it the O-ring.