Basic 2 Stroke Engine Troubleshooting And Tips

So your 2 stroke engine won't start. Maybe it's a old machine your trying to bring back to life, or a dependable engine that never lets you down. Luckily for you 2 stroke engine troubleshooting is relatively simple.

Don't worry, just follow these simple steps and we will have you back up and running in no time. If you are kicking or pulling your 2 stroke motor over repeatedly, please stop. This isn't a hot 4 stroke we're are talking about here, 2 stroke engines are very easy to start hot or cold, and hard starting is a sign that something is not right in your engine. All that kicking or pulling is just wearing out your starter and probably your leg or arm in the process.

This is all assuming that you have already checked the basics.

The 3 Critical Things To Check While 2 Stroke Engine Troubleshooting

There are really only 3 things your 2 stroke engine needs to run:

Yep, it's that simple. Now this is of course providing your engine isn't blown up with a hole in the piston or something. Typically if you can "feel" resistance in the form of compression as you kick or pull your engine over, and it's not making any horrible banging noises, it's just a matter of checking air, fuel and spark to find the culprit and get you running again.

2 Stroke Engine Troubleshooting - Air

Checking to make sure your engine is getting air is the easiest part. Typically just a visual inspection of the air filter and carburetor area is all it takes. "Air" is usually never the problem. I have only once in my life experienced air being the problem with a 2 stroke engine not starting. It was an old snowmobile that had no air filter and it had sucked a piece of plastic sheeting material that came loose from under the hood into the carburetor. Somehow the plastic had jammed just right as to not cause the throttle to stick wide open but to block the air flow into the engine. (Just a side note, never run any kind of an engine without a good air filter. Your just asking to wear out your engine prematurely or worse.)

2 Stroke Engine Troubleshooting - Spark

You might be saying, "Jim why are we talking about spark before fuel?". There are 2 reasons that we are going to check spark before we see if your engine is getting fuel:

So to check the spark we need to pull the rubber cap off the spark plug and remove the plug from the engine. I am not going to get into plug reading as that will be a seperate article in itself. For the purpose of 2 stroke engine troubleshooting, we are going to keep the plug inspection simple.

Ok, so you have the spark plug out of the motor, if the business end of the spark plug is completely caked with black crud, do yourself a favor and get a new spark plug right away. With that said, if the plug looks wet, you are getting fuel. If it looks dry, well, don't panic yet. Either way, put the spark plug wire back on the plug and lay the business end of the plug on the head (just set the plug on the metal part of the engine near the hole you took it out of). What you are doing here is grounding the plug to the engine, as if it were installed in the engine, but you want to be able to see if the plug sparks when you turn the engine over.

The engine will be very easy to spin over with the spark plug out of the cylinder, spin the engine over by quickly kicking or pulling it, you want it to spin over fairly quickly, don't pull or kick it real slow. It may require a buddy so one of you can get your head down and look at the spark plug while the other spins the engine over. We are looking for a nice blue spark across the electrode of the spark plug. If you don't get spark, try a new spark plug before you do anything else, even if the plug looks "good" try a new one.

If you have spark and the plug was dry, move on to "Fuel"

If you have spark and the plug was wet, replace the spark plug and try starting the engine again with the choke off. If this doesn't work try with the throttle wide open as your engine may be flooded (too much fuel in the cylinder). When 2 stroke engine troubleshooting and the engine is flooded, you want to spin the engine over fast with the throttle wide open several times. You should start to hear it pop, just keep pulling or kicking and holding it wide open until it starts, then rev the engine a bit to clean it out and keep it running, then warm it up properly.

If you still don't have spark with a new spark plug, you have problems with your electrical system. I won't go into any more detail on that in this article but I plan to add these types of things to this website as I have time.

2 Stroke Engine Troubleshooting - Spark But No Fuel

As you read above this is assuming you have checked the basics, you know, gas is on, gas in the tank, choke is on. One quick check you can do is to pull the fuel line off your carburetor, turn the gas on for a second and see if fuel is flowing out the fuel line. If all that stuff is ok, then it's likely at this point you have something blocking the fuel inside your carburetor. There can be several causes of this:

You have to use some common sense here. If this is a 30 year old motorcycle you pulled out of a barn somewhere, the carb will need to be pulled and comepletely disassembled and cleaned. If this is something that was running recently, and is clean with clean fuel, it may just have gotten moisture in the fuel or debris clogging up the carburetor jets. Most 2 stroke engine carburetors have an access plug or drain plug in the bowl on the bottom of them. Remove this plug (you may have to loosen the carb and tilt it to access this, or even remove the carb from the machine in some cases). Let the fuel drain out and then open the fuel valve ie. "turn on the gas" for a few seconds, it should run clean gas out the hole in the bottom of the carb at a pretty good rate. If not your float is stuck, you can sometimes "break" this loose by gently tapping on the side of the carb with the plastic handle of a screwdriver.

If you see anything remotely white colored in your fuel you have water in your gas. If you suspect you have water in your fuel, you should drain the fuel tank and start with fresh gas. Go to your nearest gas station and grab a bottle of isopropal heet, yes the stuff you put in your car gas tank in the winter. Add a bit of this to your new fuel to wick the remaining moisture out of your fuel system.

Again for the purpose of this 2 stroke engine troubleshooting article I am not going to go into any more detail, but I will be adding carburetor repair videos and ariticles on this brand new website very soon. Please check back often.

Thank You Jim Marquardt