Could be a couple of things. your carb is out of adjustment or your clutch springs are no good
How to Identify and Fix Common Gardening Problems ?
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The reason for that may be you`re using the saw at altitude or the carburetor adjustment has simply slipped. The saw also won`t operate well at speed if the air filter or spark arrestor or carburetor are dirty.
1. Dull chain and or improper lubrication to the bar and chain, sharpen and or clean the bars oil holes. 2. Air filter and fuel filter for restrictions and contamination, clean or replace as needed.
To fix the problem, start by draining the gas tank
Replace the old gas with a fresh mix of gas, being sure to add a stabilizer to keep the ethanol from gelling. Often, just getting fresh gas and stabilizer through the chainsaw`s fuel system may correct the saw and it should stay running.
The fuel line may be clogged from stale fuel deposits, more reasons to cause your chainsaw to cut out when applying throttle. If a fuel line is cracked, it will leak gasoline and draw air from outside into the fuel line. If the line is leaking fuel, it needs to be replaced.
If the filter becomes clogged, not enough fuel will reach the engine for it to run properly. Because your chainsaw will idle, but dies when it is revved up to full power, it means that the filter is only partially clogged; it will allow enough fuel to the engine to run on idle, but not enough to sustain full throttle.
If your saw idles fine, and then bogs down when pressing the throttle, then adjust your `H` screw by unscrewing. This will increase the amount of fuel to the carburetor under load. If your saw idles fine, then runs lumpy with a lot of smoke when pressing the throttle, then adjust your `H` screw by screwing in.
This could be a number of things and is most likely fuel or storage related. Over a short period of time, fuel will become stale. If the unit is stored with stale gasoline, the system will become clogged or restricted. Fuel related failures are not warranty.
If your chainsaw still starts and then stops working, check the air filter. Clean or replace the air filter if it is dirty or damaged. Another reason that your chainsaw starts and then stops working could be that the spark arrestor is dirty or clogged. If this is the case, clean it with a wire brush.
Those cutting close to the ground, muddy logs or roots of a tree (although not recommended with a chainsaw) will find their chain will blunt very quickly, those who are cutting planed softwood will find their chain will last much longer.
An engine stalls when it`s getting too much or not enough fuel from the carburetor. Stihl chainsaw carburetors usually have three adjustment screws: one each for idle, low speed and high speed. If the saw stalls while it`s idling, adjusting the idle screw, which usually is marked LA, should help.
Generally, two-stroke chainsaw engines are built to conveniently run at full throttle without an engine breakdown. Therefore, running at any throttle speed below the full throttle is not advised. Cutting a thick wood or timber while running at a low speed or throttle can cause the blades of the chainsaw to become dull.
Fuel: Make sure it is fresh and correctly mixed (see `Starting Issues`). Air filter: Make sure it is clean and unclogged. Fuel cap: Make sure it`s hand-tight. Please ensure when you are attempting to use the chainsaw that the chain brake is disengaged.
Press it up against the side of the bar and an outside tooth on your chain. When you press, is there still a gap between the bar and the straight edge? If so, you`re still in pretty good shape. With a worn chainsaw bar, pressing your straight edge against that outside tooth causes the tooth to shift over.
Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the chainsaw may run stall or run rough. To unclog the spark arrestor, remove it and clean it with a wire brush. You can also replace the spark arrestor.
If the mixture of oil to fuel is too rich, too much oil is in the fuel and it leads to the engine losing power and dying. Open the fuel cap and pour the old fuel out of the tank into a disposable container. Mix new fuel in a gas can with a ratio of 50 to 1.
The throttle and lock safety feature prevents accidental throttle engagement. Both the throttle and and lock must be pressed in order for the chain to move.