Throttle trigger will not lock - Stihl MS181 14" Chainsaw

I expect the design of your new chainsaw will be similar to many small engined tools where owners often discover they need an extra hand.

Usually the throttle is opened (trigger pulled) and then the trigger lock is pressed and the trigger released. The lock will hold the throttle partway open; freeing both hands to hold the tool steady and pull the starter. The partway open throttle makes starting easier and once started, the engine will run fast aiding a quick warmup and less chance of dying or fading.
Once the engine has warmed enough so the choke can be disengaged, a quick squeeze of the trigger will allow the trigger lock to disengage...

Terry: According to eHow.com:

"

Put on a pair of safety glasses. Remove the fuel cap from the Weed Eater and set it aside. Fill the fuel tank with unleaded gasoline that has been mixed with quality 2-stroke oil in a 40:1 ratio. Replace the fuel cap.

Move the Weed Eater to a safe place and lay it flat on the ground. Depress the fuel bulb located beneath the carburetor approximately six times to prime the engine. Press it slowly so that fuel has adequate time to traverse the fuel line.

Slide the handlebar-mounted engine "On/Stop" switch to the "On" position. Slide the choke lever beneath the fuel tank to the "Full" position.

Depress the "Throttle Lock" lever located beside the engine "On/Stop" switch. Keeping the lever depressed, squeeze the throttle trigger. Release the throttle lock. This sequence holds the trigger in the depressed position, which aids in starting the Weed Eater.

Roll the Weed Eater so that it is resting on the engine and the trimmer head shield only. This will allow the spinning trimmer head to avoid contact with the ground. Brace the Weed Eater by holding it to the ground with one hand. Using your other hand, pull the starter rope quickly until the engine begins to run. Do not pull the rope more than a dozen times. If it fails to start by then, squeeze the throttle trigger and continue to pull until the engine starts.

Allow the Weed Eater to warm up for about 15 seconds, then slide the choke lever to the "Off" position. Let the trimmer run for another minute without touching the throttle lever. After the Weed Eater has warmed up, squeeze the throttle trigger once to disengage the throttle lock. The trimmer is now operational.

Read more : http://www.ehow.com/how_6720315_start-gas-weed-eater.html"

Check to see if the throttle lock is stuck on. If it is quickly squeeze then release the trigger to take the lock off. If the trigger will not spring back you have other problems with the linkage.

The precision bent throttle connecting rod can only go in one way CORRECTLY.... if it has to be forced or bent, stop and figure out the puzzle before any damage is done.

I'd suggest placing the carb temporarily on the mounting studs on the side of the cylinder. Don't install the filter and nuts etc yet. Take the throttle rod and lay it in place this way and that way until it looks like it matches the trigger end AND the carb end. Usually the carb end has to be installed on the carb while it is removed from the engine as tightness of space won't allow moving it all over to poke it in the hole. Once it is on the carb and you are sure of the orientation, slide the carb once again over the studs and lay the throttle rod by the trigger.

You need about three hands to hold the trigger, trigger lock, trigger return spring and the handle together while you figure out how to snap in the top of the handle and start a screw under the handle.

Some saws have a throttle lock that locks the trigger to aid starting. Get a look at the carb to see if it opens when the trigger is pressed and closes when the trigger is released. If it stays open the lock may not be releasing or the throttle linkage is bound up or disconnected from the carb.

You will need to replace the trigger and throttle lock lever, they come as a pair part no. 530071305, to replace them you will need to drive out the two pins securing them in the back handle, you will also need to remove the throttle rod from the trigger.

The trigger and lock out lever comes as a kit, part no. 530071305, remove the top cover, depress the trigger and pry up the throttle wire away from the trigger, knock out the two roll pins, drop the trigger out of the bottom of the handle, lift the throttle lock out of the top of the handle.

You need to rplace the trigger, if this is a 350, start by removing the throttle lock on the top of the back handle, gently open up the slot where the latch fits, at the same time pry the rear end of the latch up, it will pop up at the back, once up pull the latch toward the back of the saw and away, now knock out the roll pin that the trigger pivots on, once out pull the trigger slightly back and down, it will just pull away, replace with a new trigger and re fit the the roll pin, push the throttle lock latch back into the tank and push the back end down to lock it into the tank, make sure the spring locates into the latch.

The two halfs of the rear handle do not seperate, once you have removed the r/h side grip you can remove the throttle lock, you then need to remove the pivot pin from the trigger with a pin punch, the trigger can then be pulled down and out, you may need to disconnect the throttle wire from the carb if you cannot drop the trigger far enough to remove the wire from it.

To remove the the trigger there is a alloy pin that needs be be driven out. Before you can take the trigger out, you need to remove the trigger lock ( dead man ) to remove the trigger lock, gently pry the two halfs of the tank apart at the rear opening where the lock sits, this will allow the back end of the throttle lock to pop up, once up pull the throttle lock toward the rear of the saw and it will come away ( bayonet fitting in the tank ) the trigger will now come out with its spring once the pin is removed.