Handling Carburetor Problems on Your Lawn Mower

If you own a lawn mower, then you know that problems arise that can affect its operation. If you don’t have the experience to identify the problems and you don’t have the skills to fix them on your own, then you have to call in a specialist to perform repairs. This means that the Saturday afternoon you have reserved to mow the lawn is shot and you will have to make other plans for the day and push back the mowing to some other weekend.

However, if you do have the knowledge to identify problems and the skills to fix them, then there is no down time and you’re assured that you can take your son to the ballgame next week.

Isn’t it best to have the knowledge to identify problems and fix them yourself?

One major culprit that can affect your lawn mower’s performance is the carburetor. If the engine doesn’t start, has idling, acceleration or speed issues, or loses power, then it is possible that the carburetor is the source of the problem. What follows are examples of things that can go wrong concerning the carburetor and what you might be able to do to fix them.

To perform the fixes you will need a socket/ratchet set, four-in-one screwdriver, adjustable wrench, needle-nose pliers, and rags. Materials you may need include carburetor cleaner, gasoline, carburetor inlet needle and seat.

Engine Won’t Start

This is a major problem that can be fixed by simply making a few adjustments on the carburetor. In this case, the carburetor is not getting the proper mixture of gasoline and air, it is dirty, its diaphragm is cracked or distorted, or the nylon check ball is malfunctioning. Fixes include:

The carburetor can be the source of many lawn mower performance problems. (Courtesy: Bob Collins)

The carburetor can be the source of many lawn mower performance problems.
(Courtesy: Bob Collins)

· Adjust the main mixture adjustment screw.
· Adjust control cable or linkage to guarantee full choke and carburetor control.
· Remove metal parts and clean the carburetor.
· Inspect the diaphragm for cracks or distortions and check the nylon check ball to determine if it is performing properly.

Engine Hunts at Idle or High Speed

This problem is due to idle or gasoline-air mixture issues or the screws and O-rings are damaged. Fixes include:

· Check idle and mixture adjustment screws and O-rings for damage.
· Adjust main mixture adjustment screws.
· Adjust idle mixture screw.
· Adjust control cable or linkage to make sure of full choke and carburetor control.
· Adjust float settings if the carburetor has a float.
· Check the sequence of gaskets and diaphragms.

Carburetor Leaks

A damaged sealing, screw, or O-ring can be the reason for this problem.

· Check idle and mixture adjustment screws and O-rings for damage.
· Check sealing of welch plugs, caps, plugs and gaskets.

Carburetor Out of Adjustment

The screws or bent chock and throttle plates may be out of alignment, the carburetor could be dirty. Fixes include:

· Adjust main mixture screws.
· Adjust idle mixture screw.
· Check for bent choke and throttle plates.
· Clean carburetor.
· Adjust governor linkage.

Engine Doesn’t Accelerate

This is probably due to a screw not aligned properly. Possible fixes include:

· Adjust main mixture adjustment screws
· Adjust idle mixture screw.

Engine Doesn’t Idle

Again, adjustment screws or control cable or linkage or float settings are not properly aligned. Possible fixes include:

· Adjust main mixture adjustment screw.
· Adjust idle mixture screw.
· Check for bent choke and throttle plates.
· Adjust control cable or linkage to assure control of chock and carburetor.
· Adjust governor linkage.
· Adjust float settings if carburetor has a float.
· Check diaphragm for cracks or distortion and inspect nylon check ball for malfunction.

Engine Lacks Power at High Speed

Adjustment screws or linkages are not properly aligned. Possible fixes include:

· Adjust main mixture adjustment screw.
· Adjust idle mixture screw.
· Adjust governor linkage.
· Adjust float settings if carburetor has float.
· Check sequence of gaskets and diaphragms.

Engine Over Speeds

Mixture screws need adjustment or seals are damaged. Possible fixes include:

· Adjust main mixture adjustment screws.
· Adjust control cable or linkage.
· Clean carburetor.
· Check welch plugs, caps, plugs, and gasket seals.

Engine Starves for Fuel at High Speed

Screws, control cable, linkage, gaskets, diaphragms, or float are not properly aligned or inlet needle and seat is damaged or not properly installed. Possible fixes include:

· Adjust main mixture screw.
· Adjust control cable or linkage to assure control of full choke and carburetor.
· Check inlet needle and seat for damage and proper installation.
· Adjust float settings if carburetor includes float.
· Check sequence of gaskets and diaphragm.

Carburetor Floods

The diaphragm, inlet needle or seat may be damaged or the nylon check ball may be malfunctioning. Possible fixes include:

· Check inlet needle and seat for damage and proper installation.
· Adjust floating settings if carburetor has float.
· Check diaphragms for damage and nylon ball for malfunction.
· Check sequence of gaskets and diaphragms.

Idle Speed is Excessive

Control cable or linkage, gaskets and diaphragms are not properly adjusted. Possible fixes include:

· Check sequence of gaskets and diaphragms.
· Check for damage choke and throttle plates.

About Robert Janis

Written by Robert Janis for LawnEq - Your specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable manufacturers.

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