2 Stroke Engine – Will Not Start

If you have 2 stroke engine that will not start, you may have one or more of the following problems:

Fuel System

  • Improper starting technique (see previous post)
  • Stale fuel
  • Dirty air filter
  • Dirty fuel filter
  • Inoperable choke/primer
  • Water contamination
  • Flooded with fuel
  • Broken/cracked fuel hoses
  • Carburetor requires repair/service

Ignition System

  • Weak spark
  • Fouled spark plug
  • Faulty stop switch
  • Faulty wiring
  • Misadjusted armature/coil air gap
  • Defective coil/armature

Exhaust System

  • Stopped up exhaust screen
  • Stopped up exhaust port


  • Low top end compression
  • Low bottom end compression


  • Improperly adjusted armature/coil air gap
  • Damaged flywheel/flywheel key (rare, but possible)

2 Stroke Starting Tips

Even when everything is working properly, 2-stroke engines can be notoriously difficult to start for those that don’t use the proper starting technique.

Here’s some simple “how to” advise:
1.) Make sure there is fresh fuel mix in the tank.
2.) If equipped, prime the carb using the primer bulb.
3.) Make sure the choke is in the “choke” position.
4.) Make sure the “On/Off” switch is in the “On” position.
5.) Open the throttle slightly so the engine will breathe.
6.) Pull the starter rope until the engine “hit’s” at least once.
7.) Disengage the choke.
8.) Start the engine!

Very Important – In order to avoid potentially severe damage, be sure to allow the engine time to warm up before going to full throttle or putting it under a work load!

* repeat the sequence above if necessary.

2-Stroke Troubleshooting Tips

Troubleshooting is nothing more than a systematic process used to test and evaluate the systems and components of an engine in comparison to an expected result. For our purposes, there are two key points to keep under consideration:

When the test results are positive or as expected, you can eliminate the area being tested as cause for concern and move on to the next suspected area.

When the test results are negative or not as expected, you should focus your efforts on the system or components being tested until the actual cause of the problem is located.

Don’t overlook the possibility that there will be more than one problem to be found with a given engine. You may locate and correct one problem, only to find others.

As mentioned elsewhere, one of the great things about a 2-stroke engine is that because everything is so closely interrelated performance wise, when you correct one problem, it often takes care of other problems without any additional work involved.

Establishing A Base

One of the best ways to improve your results when troubleshooting, is to establish a base of known factors from which you can make other decisions. While it is certainly possible to proceed without first doing this, it can make a big difference in the time you spend during the troubleshooting process. You might also be pleasantly surprised to find that many problems simply “disappear” as a result!

Below I’ve listed the things that I have found to be most effective:

  • Fresh fuel mix
  • Clean air filter
  • New spark plug

Listen Carefully…
With 2-stroke engines in particular, the ability to distinguish the different sounds the engine produces can make a huge difference in your troubleshooting! For example:
An engine that sounds “stopped up”, quite often is!

Simply by paying attention to what you hear (or what you don’t hear in this example) will lead you to an almost immediate “cure” for several potential problems caused by exhaust restriction.

Tips for successful troubleshooting:

Here finally, are some tips, learned over the course of many years, (often the hard way) that should help you through the most difficult situations…

  • Keep it simple! Always check the easier things first, working towards the more complex!
  • Never assume that a system or component is working properly. Verify it!
  • Check only one area at a time and don’t move on to something else until you’ve eliminated the system or component as the cause for your problem.
  • If you become frustrated, take a breather and walk away from the problem for a while. Don’t allow your emotion to control your logic.
  • When in doubt, refer to the proper repair manual for information and guidance.


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