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Two-Cycle Small Engine Start Up Tips

When two-cycle leaf-blowers, string trimmers, chain saws or other small engines won't start, first see if one of these common problems is the cause.

By the DIY experts of The Family Handyman Magazine

Look for fuel or spark plug problems first

Having trouble starting a balky two-cycle leaf blower, string trimmer or chain saw? Here’s what to do.

Check for a spark. If you’ve primed the engine and pulled the cord but still get no sign of life, disconnect the spark plug boot from the plug and insert a paper clip. Hold the rubber boot and move the end of the clip about 1/8 in. from the engine while you pull the cord. Look for a spark to jump the gap. No spark? Take it to a pro.

Check the fuel system. If you have a spark, check the fuel system. Remove the spark plug and examine the tip. If the tip of the plug is wet, the engine is flooded, proving that it’s getting fuel. Perform the drying procedure shown in Photo 1. Then reinstall the plug and try starting the engine again.

Try starting fluid. If the engine isn’t flooded or it still won’t start, try starting fluid. Find the air intake and remove the air filter. Spray a one-second burst of starting fluid into the air intake. Reassemble the filter and try to start the engine. If it still won’t start, that means it’s not getting any fuel. It’s time to take the unit in for professional repair.

Avoid old gas. The major reason for balky engines is old fuel. If your gas is more than a few months old, it’s likely the cause of your starting problems. Get rid of it by taking it to your neighborhood recycling center. Refill your gas can with fresh gas and add a fuel stabilizer. If you’ve been running old fuel through the engine, you may have to take the machine in to remove the varnish from the carburetor.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Air compressor
    • Air hose
    • Socket/ratchet set
    • 4-in-1 screwdriver
    • Rags

You'll also need a blower attachment for the compressor (or canned air) and a paper clip.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Starting fluid
    • Fuel stabilizer

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 10 of 10 comments
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March 14, 4:25 AM [GMT -5]

Thanks for the tips! Indeed it was very helpful.

December 07, 3:00 PM [GMT -5]

if you have trouble starting engine,take the sparkplug out and insert a hair blower to heat up the engine slightly,then put the spark plug back and try again,if it still dousnt start add starting fluid to the carberator

April 24, 2:56 PM [GMT -5]

I recently found out that there are two other factors involved in hard-starting 2-cycle engines. Neither were discussed in your article.

The first is ethanol. If possible, use ethanol-free gas.

Secondly, regular gas just doesn't "do it". Either use high test gas or add a little octane booster to regular gas.

Last summer I bought a 4-cycle Husqvarna string trimmer because my older Husqvarna 2-cycle was very hard to start, and wouldn't stay running unless my finger was on the throttle. This was in spite of a recent tuneup/repair at a dealer.

I learned of the ethanol/high test issue a month later.

I sold the 2 cycle trimmer recently, but before that, I put in some octane booster without doing anything else at all...not even a fresh tank of gas. It started FIRST PULL, and did so day after day until I sold it. Grrrr. Could have saved $300.

I then did the same thing with my Huskvarna chainsaw. Same result.

Then i tried it on my Husqvarna leaf blower/vac. I hadn't been able to even start that thing for years without MAJOR effort. SAME THING!! It's like having new machines!

Here in northern Virginia, we can't get ethanol-free gas, although it's available way out in the Shenandoah area.

Maybe this is just a Husqvarna thing, but I'll bet other 2-cycle engines would benefit as well.

Final note: I have an old (circa 1974) Homelite chain saw that always started with difficulty. I just checked and the fuel in it is gelled. I'll clean the carbeurator and lines and see what high test gas/octane booster does for that one. In the meantime, it has rejuvenated three 2-cycle engines for me!

April 24, 12:35 PM [GMT -5]

Yes this these tips would be helpful for a middle schooler with lawn mowing gigs

December 04, 1:07 PM [GMT -5]

Carberators don't build up varnish from season-to-season. Gas loses its volatility through evaporation. That's why engines have starting problems and fuel stabilizers won't solve this problem. Empty the float bowl of stale gas and the fuel tank. Put in fresh gas and the engine will fire right up--if its a fuel problem.

September 22, 11:16 AM [GMT -5]

Instead of starting fluid, use WD-40. The lubricant in the WD will prevent the piston from moving up and down in a dry condition, and the propellant in the WD 40 acts as a starting fluid. I learne this from an old smaill engine repair expert many years ago and it works great.

August 09, 8:55 PM [GMT -5]

There is a lot more to an two cycle then is said in this article.
When a 2 cycle does not start there are many factors;
1) Has gas been left in it. Gas starts to go bad in 30 days. So it is good not to make up a 5 gallons if all you have is a trimmer. If old gas is left in it over the winter most likely it is going to need a carb. kit. When old gas is left in the Gaskets and Diaphragms get hard or gummy.
2) The spark arrestor screen could be plugged. The best way to clean this is to remove the screen. Take a propane torch and heat the screen till it glows bright orange. Once it cools take a small wire brush to it. Then reinstall.
3) 2 cycle engines also need compression to start. If it does not have enough compression it will not start no matter what you do to it.
I would not recommend using starter fluid on any small engine. I would use a very small amount of gas. Don't use ethanol gas either. Ethanol is a cleaner. A 2 cycle runs at an high rpm and needs oil mixed in the gas to run. If all you can get is ethanol gas I would mix it at least 32:1 instead of the 50:1 that most 2 cycles recommend.
the article also told about spark. You can check this with a spark checker if you don't have one pull the plug and then connect it back up to the coil pull the machine over and look for a spark. This will not always tell you if the spark is at full strength. If you need to adjust the coil and don't have feeler gauges don't sweet it. A lot of time a business card will work.

July 29, 9:45 PM [GMT -5]

I just fixed my dad's leaf blower and his pressure washer...with the leaf blower, make sure the line from the gas tank going up to the carb is connected. A tell tale sign it is disconnected is an oily film all over the lower part of the blower, typically.

July 29, 9:45 PM [GMT -5]

I just fixed my dad's leaf blower and his pressure washer...with the leaf blower, make sure the line from the gas tank going up to the carb is connected. A tell tale sign it is disconnected is an oily film all over the lower part of the blower, typically.

January 30, 9:39 PM [GMT -5]

If these 4 do not solve the 2 cycle problem you may want to try these other 2 things.
1. Check the exhaust screen. These get carboned up and and need to be cleaned occasionally. Solvent and a wire brush will usually clean the screen.
2. If old gas has been left in the engine over the off season or if dirty gas has been used, the carborator can be removed, taken apart and use a bread wrapper tie (strip the paper or plastic from one end) and run the small wire through the tiny holes in the carb to remove any varnish or debris.
This carborator cleaning is slightly more labor intensive but sometimes necessary. If people would use Stable in their tank/carb or run the tank/carb dry before storing, the varnishing problems should not be a problem.

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