MS162 Tank Caps Two Caps for Two Tanks

Two caps on the same saw, similar in looks, made for two different places. The MS162 tank caps are a pair: one fuel cap and one oil cap. Both are black plastic, a wide ribbed grip, a rectangular slot in the center, and a T shaped tether on the side. The difference is in the stem: the fuel cap has a long stem with a small vent hole, the oil cap a short stem. The two do not fit each other's seats, and each cap only goes back to its own tank.

Why does the fuel cap need a vent hole? When the engine warms up, the fuel in the tank heats and the air expands. If it cannot get out, the tank swells and oil weeps at the vent. The vent hole lets the fuel cap breathe for the tank, so pressure moves in and out, the tank does not swell, and the mouth does not leak. The bar oil tank holds little fluid that changes little, so the oil cap stays simple, a short stem with a tight seal.

What is the T shaped tether for? While you top up fuel or oil, the tether hooks over the tank rim, and the cap cannot fall in or roll away. When a cap is screwed on too tight, the pull handle or a flat tool goes into the center slot for leverage, and on a chainsaw the starter pull handle is exactly the right lever.

When do the caps go? A cracked stem, a bent tether that will not hook back, grip ribs broken so the cap spins, the pair goes together. Fuel weeping around a tank mouth points at the cap seal first. This pair is made for MS162 tank seats. The MS172 from the same generation is listed as a common fit in some places, but that has not been verified one by one, so compare the old cap size and the tank seat, or send a photo before ordering.