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How to adjust carb on a 27cc 71120 craftsman weedwacker?

It bogs down at half throttle. and since it is speed start there is no choke. where are the adjustment screws?

Posted by Anonymous on


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Posted on Jan 02, 2017

  • 246 Answers

SOURCE: carb adjustment


>>The Following is the Instruction File for Setting the Air Mixture Screws. Any Input is Appreciated. The Procedure is the Same for 1 or 2 Mixture Screws, Just Use the Instruction File and Skip Over the Section with the Missing Mixture Screw ( Usually the H Mixture Screw).
>>Now Setting the Air Mixture Screws:
>>****Turn the Idle Air (L) and Main Air (H) Mixture Screws In Until SNUG **Do Not Jam** Then Reverse Both Screws 1 1/2 Turns. Set the Throttle Full Open, Start the Engine.
>>Turn the Main Air (H) Mixture Screw Clockwise Until Proper Revs are Obtained. **Carefully Use your Finger and Move the Governor Arm to Rev the Engine (on Chainsaws and Trimmers Use the Trigger to Rev the Engine) Until you Reach Max RPMs (on Chainsaws and Trimmers, the RPMs are Not Set to MAX. Set to Max and then Reverse the Setting Screw 1/4 or 1/2 Turn. If the H Mixture Screw is Set too High; the Engine will be Starved for the Oil in the Gas and Damage the Piston and Jug/Cylinder) and the Engine is Running Proper at Full Throttle Up a Grade. Occasionally you May have to Turn this Counter Clockwise to Achieve the Proper Revs.**
>>Now Allow the Engine to Idle. Set the Engine Idle Screw (Not Idle Air) so the Engine will Stay Running if Required.
>>Now Set the Idle Air (L) Mixture Screw so there is No Hesitation when Rapidly Throttling from Idle to Full Throttle. Reset the Engine Idle if Required.****
>>If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy.



Posted on Apr 21, 2009

  • 173 Answers

SOURCE: Craftsman blower stalls when choke is disengaged

You need to play with the timing adjustment, either on the spark plug, or the gap between the contact and the magneto.
That'll do it ;)
Don't forget to rate, thanks

Posted on Aug 01, 2009

  • 1 Answer

SOURCE: Echo PB-413H bogs down

Echo tools have a screen in the muffler to arrest sparks. Take off the muffler and remove this screen

Posted on Aug 12, 2009

  • 16 Answers


Check the carb jets, they might be a gummed up!

Posted on Aug 25, 2009

  • 1 Answer

SOURCE: craftsman gas leafblower

I just worked on my craftsman leaf blower that would only run at half choke. I tried cleaning the carb and also cleaned the exhaust port. Didn't help. Then i took the cover off and noticed that one of the head gasket bolts was loose. Tightened the head gasket bolts and then it ran fine. Must have been sucking some air.

Posted on Aug 01, 2010

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1 Answer

What will cause newish sears 27cc string trimmer only run on full choke?

If the trimmer has been sitting for a long time it is probably the carb needs to be rebuilt. Before doing that check the plug and be sure you are getting fire. Be sure nothing is blocking the fuel filter in the tank. Be sure exhaust or muffler is not plugged, with only 5 hours on the trimmer I wouldn't think that is the problem. Sound more like something in the carb. You can look on you tube to see how to rebuild the carb if you have not done it in the pass it is fairly simple to do.

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Runs only on half choke

Before you take it a part adjust the fuel air mixture most of these small engines are air 1 1/4 and fuel 1 turn get it to ideal just before the foot spins ( let the engine warm up good and have fresh fuel before doing these adjustments) afer a good ideal adjust the mixture for a full no bogging speed . If this does not work then start to work on the carb.

Jul 20, 2012 | Garden

1 Answer

My craftsman weedwacker 316.791190 bogs out at full throttle. i cleaned air filter, plug, carb, it runs great when i cover the air box with my hand though,

When you cover the air bos, you are in essence, enriching the air/fuel mixture that is entering the engine. The carburetor does this when it is needed and when it is functioning properly. For the bogging problem, it is evident you need a small carburetor adjustment. I suggest turning the L mixture screw (the one on the carb closest to the engine) out (counterclockwise) 1/8 to 1/4 of a turn. The heads of the L and H mixture screws are unconventional type and some improvising will have to be done to enable you to get ahold of them to adjust them. I use a small plastic (22 gauge) automotive-type wire connector with a ring terminal end on it. I tap it down onto the screw head with a small ball peen hammer until it stretches around it. I then am able to turn it. Try the suggested adjustment for your high-speed bogging problem. And to further tune and adjust the carburetor on your machine, I highly suggest you look at the following tutorial.

May 22, 2011 | Craftsman 27cc 2 Cycle Crank Straight...

1 Answer

Is there a idel scrwe for craftsman 26.2 cc weedwacker

The 2 stroke engine on your machine has a diaphragm carburetor with 3 carb adjusting screws. The small Phillips-head one adjusts your IDLE speed as it pushes against the throttle plate lever that the throttle cable is connected too. Turn it in, the idle speed increases...out, it slows down. This screw is on the exterior of the carburetor. Now there are also 2 adjusting screws that meter the amount of fuel that goes through the L (idle) and H (high speed) fuel circuits. They typically have odd ends on them to make them "tamper-proof" per EPA regulations in the US. You can acquire or make a tool to turn them with. Ebay has them. A word of advice. If you machine won't "throttle-up" satisfactorily, then turn the L screw (stamped on carb body) out about 1/4 of a turn. That sometimes cures the "bogging-down" acceleration issue many people encounter. These carbs are very sensitive, so don't "play" with the settings too much. See this instruction sheet from a main carburetor manufacturer. Hint: I jam small automotive-type plastic wire connectors on the screw heads to turn them.

Feb 01, 2011 | Craftsman 25cc Gas Line Trimmer

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Manual for a craftsman weedwacker model 31679108

Trimmer Starts but stall out as soon as throttle is used and choke turns off. if I hold the throttle and pull the choke it runs but will stall as soon as choke is let go.

Jan 31, 2011 | Craftsman 27cc 2 Cycle Crank Straight...

1 Answer

Craftsman 25cc weedwacker (358.791030). Zama carburator (C1U-W19) Just rebuilt carb but did not adjust low speed/high speed screws. Starts on first pull (with choke lever actuated), and after warm up,...

need to adjust the high sscrew. i do mine in 1/4 turns. start machine, full throttle, adjust the h(high) til it clears up.i would start by turning 1/4 counterclock wise, just remember to keep track, in case it runs worse, the put it back to orig. then try the other way. but i suggest 1/4 turn at a time

example... think of a clock when turning screw. straight up and down, 12oc, 1/4 turn will be 3oc, another 1/4 will be 6oc, and so on. hope it helps!

Sep 17, 2010 | Craftsman 25cc Gas Line Trimmer

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