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Ho To Fix A Trimmer That Doesn't Stay Running

by HIPA Jeremy 20 Sep 2022 0 Comments

It is a common problem that trimmers do not stay running. Here is a general guide on how to fix it.


The first thing you need to check is the fuel. Make sure there is no water in the fuel. Press the purge bulb and try to start it.
If it can successfully start but still fail to run, it could be a carburetor issue.

Valve lash

Now you need to adjust the valve lash that is the clearance between the rocker arm and the top of the valves. The clearance is very important when it comes to the timing of when the valves open or close. So you have to remove the top cover followed by the valve cover and put one of the rocker arms in the down position, then check the other rocker arm to see if the valve lash is out of spec.
With the exhaust rocker arm in the down position, you can use a gauge to feel how it fits in the clearance between the intake rocker arm and valve after sliding it into the clearance and moving it around. If you do not feel any drag on it and it is really easy to move around, that is telling you that the clearance is larger than the gauge and it needs to be adjusted.
After putting the intake rocker arm down, you need to do the same procedure to another rocker arm. Then put everything back together and try to start it.


If unfortunately it do not start, you can try to turn out the high and the low speed screw on the carb.
Use the little screwdriver to slightly turn the high-speed screw and the low-speed screw in until they are lightly seated, and turn both of the screws back out 1/4 turn. (Small tips: do not screw them in so tight that it may damage the carburetor. )

The High-Speed Screw

We will start with the high-speed screw rather than the low-speed screw on a string trimmer. However, low-speed adjustment is the top priority on chainsaws.
1.Press and hold the trigger down to run as fast as it can.
2.Use the little screwdriver to turn the high-speed in and out until you find the spot where the string trimmer running the fastest.
3.Unscrew the high-speed screw slowly until you hear the RPM (revolution per minute) start to drop, then turn the screw back in again until you hear the RPM just come up to a position where it is making the humming sound.
That is the ideal position of the high-speed screw.

The Low-Speed Screw

1.Here, you do not need to hold on to the trigger, you just need to leave it at idle. If the string trimmer does not idle, you just need to turn the low-speed screw in until it idles.
2.Similar to the high-speed screw, turn the low-speed screw in and out until you find the sweet spot where the string trimmer idling the fastest.
3.Turn the low-speed screw out very slowly until you hear the RPM just start to drop.
4.Leave it there, do not turn it back in.
You will receive an excellent trigger reaction when you punch the trigger again.
By the way, you’d better check if the carb is leaking fuel especially when pressing the bulb, replace the carb if necessary. Check the fuel flow after you put on the new carb, then put all things back on and try to start it.


Please let us know if this works and if you have any suggestions or comments. Or you can join HIPA DIY COMMUNITY to feature your passion for repair projects, share your stories with the Hipa family and get help from Hipa.

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