Small Engine Troubleshooting: Fix Your Lawn Mower, Chain Saw, or Leaf Blower

If you're an absolute beginner, learn how to diagnose common small-engine problems and fix the ones you can, including what to do if you have a broken crank rope.

| May/June 1989

  • 117-096-01-pixa
    With a little know-how, you can soon learn how to diagnose and fix common problems with your lawn mower's engine.
    PHOTO: WILLIAM WALDRON
  • spark plug hooks diagram compressed
    Spark plug hooks in the Tecumseh (L) and Briggs (R) engines.
    KAY HOLMES STAFFORD
  • testing a spark plug diagram
    Testing a spark plug.
    KAY HOLMES STAFFORD
  • Gapping a Spark Plug Diagram
    Gapping a spark plug.
    KAY HOLMES STAFFORD
  • electronic ignition flywheel diagram
    The electronic ignition is a little plastic-enclosed box or disk almost touching the flywheel.
    KAY HOLMES STAFFORD
  • freeing a flywheel diagram
    Freeing a flywheel.
    KAY HOLMES STAFFORD
  • points and condenser diagram
    Points and condenser.
    KAY HOLMES STAFFORD
  • locking a flywheel diagram
    Locking a flywheel.
    KAY HOLMES STAFFORD
  • gapping a CDI diagram
    Gapping a CDI feeler gauge.
    KAY HOLMES STAFFORD
  • Tecumsah float bowl diagram
    Tecumseh float bowl.
    KAY HOLMES STAFFORD
  • Briggs clog spots diagram
    Briggs engine clog spots.
    KAY HOLMES STAFFORD
  • shaft key diagram
    The shaft key is a little rectangular or half-moon metal piece that aligns the flywheel on the crankshaft.
    KAY HOLMES STAFFORD
  • Tecumsah float valve
    Tecumseh float valve.
    KAY HOLMES STAFFORD
  • cleaning an air filter diagram
    Cleaning an air filter.
    KAY HOLMES STAFFORD
  • holding the choke open diagram
    Holding the choke open.
    KAY HOLMES STAFFORD
  • rigging the governor diagram
    Rigging the governor.
    KAY HOLMES STAFFORD
  • sheared shaft keys diagram
    Sheared shaft keys.
    KAY HOLMES STAFFORD

  • 117-096-01-pixa
  • spark plug hooks diagram compressed
  • testing a spark plug diagram
  • Gapping a Spark Plug Diagram
  • electronic ignition flywheel diagram
  • freeing a flywheel diagram
  • points and condenser diagram
  • locking a flywheel diagram
  • gapping a CDI diagram
  • Tecumsah float bowl diagram
  • Briggs clog spots diagram
  • shaft key diagram
  • Tecumsah float valve
  • cleaning an air filter diagram
  • holding the choke open diagram
  • rigging the governor diagram
  • sheared shaft keys diagram

Ah, spring, time to get outside and do. Cut that grass! Turn that soil! So you roll the old lawn mower or rotary tiller out of storage, give the crank a couple of vigorous pulls—and a few more pulls—and a few more pulls—and then start cursing. "The !&@*!! thing won't start!"

What now? If you're already a shade-tree mechanic and know a few things about small engine troubleshooting, you hunker right down and start tinkering. But, if like me (a certified carburetor klutz) you're frankly intimidated by that mishmash of wires, hoses, valves and levers, you probably just keep doing the only thing you know how to do: Yank the crank. A few dozen pulls later, your arm's sore and your temper's shot. Defeated, you roll the renegade yard-aid back into the shed and storm into the house. One perfect spring day—ruined.

Your options now? Either hope the machine'll change its mind and crank up the next time you take it out, or haul the blamed thing off to a repair shop. You'd probably take it to a shop right away except for that nagging fear that the malady is some simple little thing that any nitwit should know how to fix—and that your mechanic will be only too glad to point this out.

If this scenario sounds familiar to you, read on. The purpose of this article is to help you learn how to diagnose common small engine problems, fix the ones you can and toss up your hands gracefully when you can't. It's based on the hands-on know-how of Dennis Burkholder, MOTHER's own workshop wizard. In his 13 years with MOTHER, our "Mad Swede" has had to build everything from a supposedly perpetual motion machine ("a perpetual headache machine," Dennis called it) to a leaning, three-wheeled automobile. Before coming to us he did such things as help design lawn mowers and even test-drive snowmobiles. The man knows engines inside and out.



Before we begin, I need to share a confession, define a few parameters and offer a bonus.

The confession: We can't begin to cover all small-engine models and problems. We'll just hit some common small engine problems that almost anybody can treat—by following a logical troubleshooting sequence through the engine. Maybe these steps will help you shake off any timidity and get you interested in exploring and learning more. (There are plenty of good books and mechanics to guide you.) But even if you go no further than the steps we've outlined, we're betting you'll be able to fix the great majority of start-up troubles that strike your small engines.

Darryl
4/13/2016 4:55:37 PM

I acquired a new looking 1733cc Cub Cadet mower that had been sitting out in weather for more than a year. I put fuel in the empty tank and it started on first pull ran for 3 seconds then died. Since then I have: replaced spark plug, air filters and carburetor(brand new). I also made sure there is fuel freely flowing in fuel line to carb, removed and replaced oil and still it starts on first pull runs for 3 to 5 seconds max then dies. I took it to a pro who has been repairing small engines for 50 years. A week later he calls me to come pick it up. He gave up on it and says this is the first engine he can not fix. It still has same problem. What can possibly be the matter with this engine?







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