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I have a McCulloch string trimmer w/ a Walbro WT434 carb. I replaced the fuel filter, fuel line, metering diaphram, fuel pump diaphram, gaskets, etc. The trimmer will start but will not accelerate unless I close the choke. with the choke closed, it will accelerate momentarily until the engine dies. So, it seems like it is not getting enough fuel and i'm not sure what to do. I was going to remove the limiter caps for the hi (or lo) speed adjusters, but I'm not sure how or if they come off. Any ideas?

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6ya6ya
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Posted on Jan 02, 2017

  • 52 Answers

SOURCE: String trimmer, fuel lines disintegrated, I need routing.

The Walbro has two connections on it for the fuel line. My Walbro has one connection on the side of the idle screw and main fuel adjusting screw. This connection hooks up to the suction side of the primer bulb. Usually the shorter stem. (You actually **** fuel through the carb instead of pushing it through.) On the other side of the carb is the other hook up. It draws fuel from the tank. This line will connect to the side of the tank that has the filter. The other side of the tank is your return and it hooks to the other connection on the primer bulb. Usually the longer stem.

Posted on Apr 19, 2010

mighty thor
  • 51 Answers

SOURCE: Sputters & quits at proper RPM for engaging trans or mowing deck

If the choke has an adjustment point, then adjust the choke to a good overall working powerband. If it still doesn't act correctly, look for vacuum leaks. If it is an option, you may want to install a manually operated choke lever.

Posted on Nov 24, 2008

  • 4 Answers

SOURCE: Mcculloch 3216 starts few seconds and dies, choke must be closed.

after jerkin fingers bloody today same problem i took carb apart,,the old hoses deteorated an clogged screen on in take side/// inside of carb plate //of carb,,blew out with choke cleaner,, reassembled now runs well make sure to run same size hoses large an small,,as original other wise floods out,,,

Posted on Mar 21, 2009

  • 109 Answers

SOURCE: Snapper SS312 weed eater. Cranks when primed but won't run

I am sorry to say this, but the compression for that type of engine should be atleast 120 psi. Remove the muffler and look at the cylinder, it is scarred beyond repair.

Posted on Apr 22, 2009

  • 246 Answers

SOURCE: Engine will only run on 1/2 Choke

Hello edv40026:

Have you Checked the Exhaust Port and Muffler for Restriction?
From your Description it Sounds like the Exhaust Port or Muffler is Restricted with Carbon Deposits, the Carburetor Metering Pump Actuator Gap is Incorrect or the Compression is Low (Worn Rings/Cylinder).
>>The Following is a Basic Instruction File for Doing a Diagnostic on the Engine for this Problem. Any Input is Appreciated.
>>**Remove the Muffler and Make Sure the Exhaust Port is Clear.
>>If it is, then Try to Start the engine with the Muffler Off.
>>If it Starts and Runs Properly, then Clean the Spark Arrestor Screen in the Muffler or Replace the Muffler if Required.
>>The Following is a Basic Instruction File for Doing a Diagnostic on the Engine for this Problem. Any Input is Appreciated.
>>**Remove the Muffler and Make Sure the Exhaust Port is Clear.
>>If it is, then Try to Start the engine with the Muffler Off.
>>If it Starts and Runs Properly, then Clean the Spark Arrestor Screen in the Muffler or Replace the Muffler if Required.
Is the Fuel Line from the Fuel Filter Staying Full of Fuel?
The Carburetor Metering Jet Actuator is Set so the Pump Diaphram Dowl is Just Touching the Actuator Arm. These Components are Located Under the Cover with 4 Small Screws Holdong it to the Carburetor Body.
Please, Do Not Hesitate, 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 Be Happy. Thanks.

Good Luck

Respectfully

jbridger (John)

Posted on May 13, 2009

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Trying to rebuild a WT 185 carb for a weedeater. I have the kit. Need a diagram, PLEASE.


hi there drainmasters

here is web site link to help with intstructions

http://www.ehow.com/how_4869458_rebuild-walbro-carburetor.html

your carb kit would be a k20-wat

be sure to get everything in the correct order

ie fuel pump is the side with 1 large screw ,fit the fuel inlet screen fit the diaphram 1st then the gasket and cover

the other side is the metering diaphram , make sure the metering lever is set flush with chamber floor and then fit gasket , then diaphram then the cover

make sure the hi and low needles are back where they came from and set lo and hi to a base setting of 1- 1/4 turns out from lightly seated

check out the web site it will help

cheers pauly46
k20-wat.jpg

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Start with the easy things first, pull the fuel hose from the tank and replace the filter on the end, check the fuel hose up to the carb for cracks or splits, the carb has two diaphrams, a metering diaphram, which controls the amount of fuel in the carb, much like a float bowl on a normal carb, and a pump diaphram, which pulls fuel from the fuel tank, into the carb, these two items have a long service life, if they have aged or the material attacked by the fuel they can become stiff and not work very well, however i think it unlikley that the saw would not actually start, it may run bad, but it should start.

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Do you have a diagram that shows where all the fuel lines on a MAC 2337 string trimmer go? There are two places on the carburetor (Walbro 312) for fuel lines to go, two fuel lines coming out of the fuel...


The small diameter line out of fuel tank (has filter in-tank on end) connects directly to the side of the carburetor that has the fuel pump....that is the cover without the hole in it. Other larger diameter fuel line out of tank connects to the longer nipple on the external purge/primer bulb. The bulb "pulls" fresh fuel from the fuel tank to the carb and then out of the carb to itself, where it then "pushes" any air/old fuel back into the fuel tank. The remaining larger diameter fuel line in this setup goes from the metering chamber (has cover with writing on it and a vent-hole) side of the carburetor to the smaller nipple on the purge/primer bulb. Again, on the primer bulb, the longer nipple has a line going directly from it to the tank. This is the return line. The shorter nipple on the bub has a line from it going to the metering chamber side of the carb. If the purge/primer bulb is on top of the carb...small line from carb body to small hole in tank with filter. Larger diameter line goes from the bulb on the fuel pump side of the carb to the larger hole in the fuel tank where sometimes the line is held in place with a nylon nipple connector that keeps the line from pulling out of the tank. Otherwise, the line should enter the tank for about 1/2" or so.

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1 Answer

I've replaced the fuel lines and installed a carb rebuild kit on my Weedeater GHT 225 hedge trimmer and it still dogs out when I try to get it to full RPM's, sometimes even half choked. The spark plug and...


My best guess is that you replaced the internal parts of the carb, but you did not clean it and adjust it well enough. Take the carb back off and clean out all of the passages with aerosol carb cleaner. Remove each of the adjustment screws and blow cleaner through them as well. Reset them by turning them gently clockwise until they seat, then turn counterclockwise 1.5 turns each. This is a good starting point. Make sure the needle arm in the carb is set at the correct height. If you have a Zama carb, you can use a straight edge to set the height. Lay the edge across the carb (where the diaphragm will be) and check to see that the needle arm is just even with the edges of the carb.. If you have a Walbro carb, you will need to get the Walbro tool (WB 500-13-1) to get the needle arm set to its proper height. An arm that is set too low, will starve the engine and one that is too high will flood it. Also make sure the gaskets are installed in the proper order. Diaphragm side, the gasket goes on first, then the diaphragm. On the metering plate side, the metering pump goes on first (thinner one) then the gasket goes on, then the outer plate.
Don't forget to replace the inlet strainer (small screen).

On to fuel lines. You Weedeater product uses 2 sizes of fuel line. The smaller line must connect to the fuel filter in the tank, and then to the fuel port on the carb that is opposite the diaphragm. The fuel port that is closest to the diaphragm will connect the larger line. This is a return line and will go back to the tank. It may or may not have a small fitting on the end of it in the tank.

Now try a test run again. If it will idle, but not rev up, open up the Lo adjustment screw (closest to the engine) by turning it counterclockwise 1/4 turn. Test run. No change? go another 1/4 turn. If after all this, it is still not running properly, then there is a fault in the carb and it will need to be replaced.

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String trimmer, fuel lines disintegrated, I need routing.


The Walbro has two connections on it for the fuel line. My Walbro has one connection on the side of the idle screw and main fuel adjusting screw. This connection hooks up to the suction side of the primer bulb. Usually the shorter stem. (You actually **** fuel through the carb instead of pushing it through.) On the other side of the carb is the other hook up. It draws fuel from the tank. This line will connect to the side of the tank that has the filter. The other side of the tank is your return and it hooks to the other connection on the primer bulb. Usually the longer stem.

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1 Answer

String trimmer won't start. How do I flush the


To flush system
Drain tank, use primer bulb to push out fuel in the lines, refill, use primer to bring in fresh fuel. You may need to pull the rope a few times with the choke on, and then push the primer several times again. Sometimes you may need to put a few drops of fuel into the throat of the carburetor to help it start to fire.
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