DIAGNOSIS That’s a frequent observation. The oil flow adjustment on this model is subtle, especially if you’re looking for a dramatic change. It’s not a valve, it’s a limiter that changes the stroke of the automatic pump. The difference is often between “a lot” and “a whole lot” of oil.
FIX To really see if it’s working, you need a controlled test. Put in a fresh bar and chain oil, mark the oil level, and make a series of identical cuts (like a 6-inch log) with the screw turned all the way to the minus/minimum setting. Note how much oil you use. Then refill to the exact same level, turn the screw all the way to the plus/maximum setting, and make the same number of cuts. You should see a measurable difference in the oil level drop the second time.
IF THAT DIDN'T WORK If you truly see zero difference—like no oil at all on minimum and a flood on maximum—the adjustment mechanism might be broken or disconnected inside. The screw turns a small cam that acts on the pump lever. It’s rare, but that linkage can fail.
HEADS UP The factory setting is usually near maximum. In dusty conditions (cutting dry, pressure-treated wood) you want max oil. For cleaner, green wood, you can turn it down to save oil and reduce mess. But if you’re cutting anything abrasive, like dirty wood or wood near soil, always err on the side of more oil to protect your bar and chain.