Carburetor Needle Valve and Seat Replacement

April 26, 2011



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Machine type:  Tecumseh powered snowblowers, lawn mowers, chippers and riding mowers.

Brand:  Primarily Craftsman, but also many others

In your efforts to keep your equipment running seamlessly, you will often find that you need to service the carburetor.

A float type carburetor depends on a good seal between the needle valve and the valve seat. This seal closes and allows the flow of gasoline into the float chamber as the engine consumes it.  If it sticks open, the engine will get too much fuel and will run very rich.  Gasoline will also be seen running from the carburetor even when the engine is not running. If it sticks shut, no fuel will get into the carburetor and your life will not be happy, at least if you like getting your lawn mowed.

Let’s get that carb working:

  1. Remove the center bolt from the float chamber. This is often a 7/16” or a ½” size. Tug gently on the float chamber and remove it.
  2. Pull the pin out that holds the float in position. Notice that the clip holding the needle valve and the needle valve come out with the float. The position of the clip is important. It should have its open side toward the air intake side of the carb.
  3. The valve seat is up inside the hole between the float mounting points and the center casting of the carb. I use a special tool that looks like a darning needle on one end to pull the old valve seat out.  I have also used compressed air into the gas inlet. If you use this method, put a piece of shop towel over the hole. This keeps the rubber piece from coming out like a rubber bullet. Trust me on this one. Another method I have used is to carefully thread a course screw into the rubber and pull it out that way.
  4. When the rubber is out, I give a blast of carb cleaner up into the hole, and then some compressed air to dry and clean the area.
  5. Notice the package from RepairClinic.com. It has both the needle valve and it’s clip, and the new seat. The seat has a smooth side and a side with small round ridges. Put the ridges up into the carb first. I use the special tool to hold it and put it into place. Another method is to take a drill bit that is just smaller than the hole and use that to guide the rubber seat into place.
    Needle Valve and Seat Front

    Needle Valve and Seat - Front of Package

    Back of Package

    Back of Package

    Seat on tool

    Seat on tool

Then just assemble the float, its clip, the pivot pin and the float chamber bowl as you took them apart earlier.

These are two ways to get the parts.

  • You can just buy the needle valve and seat: 1659221 for $4.95 plus shipping.

    Carburetor Inlet Needle and Seat

    Carburetor Inlet Needle and Seat

 

  • Or you can get those parts plus a bolt gasket and a bowl gasket. Item #1606506  for $4.35 plus shipping.

    Carburetor Needle Rebuild Kit

    Carburetor Needle Rebuild Kit

The second choice is a better deal and a lot less frustrating than trying to get a float chamber bowl back on when the ring gasket has either fallen out because it has swollen or has been pinched and is no longer sealing.

You will be glad you learned how to make this simple repair. You will benefit from it if the needle valve was the problem, and you will have eliminated a common failure point if it was not in fact the cause of the trouble.
Small Engine Parts

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