Small Engines (Lawn Mowers, etc.): Homelite 330 chainsaw, walbro carb, engine crankcase

Question
QUESTION: I was given a Homelite 330 UT10609. It did not run. Cleaned the Walbro carb. The gaskets and diaphrams seem to be in good condition-no warping or wear patterns. Set the float to level with carb body as per spec. It did not start. It was not pulling gas into the carb. I reset the float tang to higher than spec. Saw starts but runs at very high rpms with little surging. Thinking the carb was sucking air I coated the gasket ( on both sides ) that sits between the carb and the housing with semi-harding permatex. Saw still runs at full throttle. Playing with the high-low needles has no effect as does playing with the idle screw. Butterfly is not bent and the linkage moves smoothly. Choke works as it should. Other than replacing the carb I hope you have the answer. I have an xl-12 and replaced the carb with a Zama with not so good results. Luckly I found an original. Thank you, Charles.

ANSWER: If the metering diaphragm, the one that moves the inlet needle, is stiff you make have some running issues.  Sometimes you can hear a stiff diaphragm krackle as you move it.  The diaphram, actually both diaphrams, should be soft and plyable, you should be a bend and twist them easily.  Carb kit should be around $15.  330s were good saws and very reliable...I would get a kit.

As for the full throttle running it must be the trigger link rod causing the problem or the carb butterfly is open too far.

Dis-connect the throttle link and turn the idle screw all the way out to see if the saw still runs at full throttle.

Be carefull with the gasket sealer on the carb housings.  There is a little hole on the face of the carburetor that get a pulse from the engine crankcase.  This pulse operates the carburetor fuel pump that pumps fuel into the metering side of the carb.

Let me know if the engine speed slows down when you disconnect the throttle.

Eric

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QUESTION: Rebuilt carb with no luck. Now the saw refuses to start. Disconnecting throttle has no effect. Whiped off permatex. Saw still refuses to start.I did rebuild correctly. There are only two diaphragms and two gaskets to replace. Inlet needle is new. Screen is clean. Could the carb be worn out?

Answer
Do you still have ignition?  Did you make sure you had the diaphram and gaskets install correctly?

On the fuel pump side the diaphram usually goes on first, on the main carb body, then the gasket.  The metering side is different, the gasket goes on fire, next the the main carb body, and then the diaphram.  Is the metering lever arm set to the correct height.

Did you check out the carb manufacture's website link?  Walbro, Zama, and Tilliston have online maintenance manuals.

Rarely do I find carbs wore out unless someone screws in the adjustment needles too far.

Let me know if you still have spark.

Eric