2-Cycle Engine Tips For Weed-Whackers / String Trimmers, Chainsaws

Guest article by ‘Calirefugee’

[ Ken adds: ‘Calirefugee’ spent many of his younger years fighting wildfires in the wilderness areas of the Sierra Nevada Mountains ]

Hints to keep your 2-cycle engine running

For chainsaws and weed-whackers/string trimmers:

Treat it right

#1 Do not abuse the tool. It can be frustrating when that 2-cycle engine will not start. It may be tempting to bounce them on the concrete driveway! DO NOT abuse your tool (they are expensive).

Store the 2-cycle engine dry

#2 Store the 2-cycle engine dry. At the end of a job, I will shut down the engine, drain fuel into the fuel can, and run the engine dry. After the engine cools, I then store the tool dry.

Use the best fuel for 2-cycle engines

#3 Try to use the highest octane, “fresh” fuel you can obtain with minimal amount of ethanol in the fuel. Along with that, carefully follow the instructions on mixing of engine oil with fuel. Some 2-cycle engines require a mix of 1/32 oil to gas mix, while other tools require a 1/40 oil to gas mix. Ultimately, consult the instruction manual. As far as where to get “good fuel” for your chainsaw or power scythe, ask at the store where you buy/bought your tool.

The Most Popular Fuel Stabilizer
(view on amzn)

Most Popular 2-cycle Engine Oil

“It has numerous markings for different fuel : oil ratios for accurate mixing (a gallon). Loosen the cap and squeeze gently until the desired amount is reached. You might use a sharpie to highlight the markings to make it easier to read.”

Spare, Gapped Spark Plug

#4 Carry a spare, gapped spark plug and the tool needed to pull and change out the spark plug with you into the field or job site. If you flood the engine, pulling the plug can get you back in action faster.

Sandpaper

#5 I will carry a small piece of sandpaper with me to clean the plug. Because sometimes, varnish from fuel can form on/between the contacts.

Warm up before applying full power

(extracted from Bill’s comment below)

Biggest way to increase the life and reliability of chainsaws, mowers, blowers and whackers is to let them warm up a good bit before applying full power. Failure to do this often lead to “cold seizures.”

What happens, is a cold chain saw is started and then almost immediately is pushed to full power cutting a log. The piston has far less thermal mass than the cylinder and will heat up much faster under the sudden full power.

The piston consequently expands faster than the cylinder and the clearances between the two reduce. This causes much accelerated wear on the piston, rings and cylinder and can trash the engine quite prematurely.

Always allow a cold engine to gently warm up to full operating temperatures before applying full load/power.

Many have gone over to electric power tools these days. Yet there are many good 2-cycle power tools out there being used a lot at this time of year.

I like to work on the power tool in the garage or barn and run the thing with a fresh batch of saw gas mix prior to going into the field or the job site. (Although my years fighting fire with 2 cycle engine power tools are long since over.)

My parents bought Stihl brand tools and the Tree service I worked on we used a bunch of different brands: ( Echo, Poulan, Stihl, Husquavarna, Homelite, Sears ).

In the end, I preferred using Stihl tools because there was a service center near my folks place where the proprietor gave me all of the above hints to keep those expensive power tools running for years.

Dedicated to Sam at Apex sharpening and power tools in California.

[ Read: Run Your Generator Several Times A Year – What You Should Know ]

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21 Comments

    1. Absolutely. That’s huge! Fortunately there’s a gas station not too far from me that has one pump with Ethanol Free Gas. I fill all my gas cans there. Plus, I do use PRI-G stabilizer.

      1. Non ethanol fuel is the only thing that goes in any of my small engines. Wont use anything with ethanol in it at all.

  1. Personally I use only Non-Ethanol fuel in all my small engine units, yes Mildred even those clunky old 4 cycle things….

    Secondly only use Stihl 2-cycle oil mix in a Stilh. Note: If a Stilh takes more that 2 pulls to start it, get it fixed heheheeh….

    Third, Premium Gas in ALL gas vehicles, yes it’s a little more expensive, but it’s a LOT less Water (Ethanol) that regular and the extra HP you’re going to get is more that the extra cost of the fuel. especially if you have an older vehicle, YES Ethanol will rot out the old fuel lines….

    Lastly, who the HELL decided to use Food (corn) to make Gas? Sounds like a completely insane idea don’t it? Take Food off the tables end stick it into your Gas Tank…. Yeppers, we have all gone completely NUTS!!!

    1. I don’t know who made the decision but the ethanol lobby has been around at least since the 70’s. I believe it happened in Bush seniors term. The ethanol was used to replace MTBE (methyl tertiary butyl ether) as an octane enhancer in spite of the negative attributes overall which include a negative energy balance and fouled fuel lines. I believe the other effect was that the excess grain that had been sent to the mideast and north Africa for food is now being consumed in our cars. I believe it contributed to the so called “Arab spring”.

    2. I’m not a salesman, but I’ve also had the best results with Stihl products and their expensive 93 octane pre mix gasoline.

    3. The wizards that decided to make fuel out of food are in control of our country. We are in deep doo doo.

  2. Calirefugee,
    Thanks for your tips and reminders on small engines. I have an Echo (25 years) and a Stihl (4 years) both good saws.I do use my 18 volt Makita recip saw with a pruning blade for a lot of small stuff and even fell some 18″ pine trees with it.

  3. Reply to NRP and Blue:
    It generally takes me more than 2 pulls to get a 2 cycle going even after I have primed the engine with fuel, set the choke. Butt, I agree, on a well maintained and properly stored 2 cycle engine, I can get it started within 5 pulls of the cord. ( starting out cold engine from storage ).
    If it does not, I pull the plug and inspect the contacts for varnish or carbon build up on the contacts or a cracked ceramic insulator. This I do prior to taking the power tool back to the shop for repairs. Lastly, high RPM’s when in use tend to eliminate the carbon buildup and storing the tool dry tends to reduce or eliminate the varnish on the plug contacts.

  4. “It may be tempting to bounce them on the concrete driveway!” This makes me laugh!

    I had a Toro 2-cycle blower I bought at a yard sale. It was supposedly “never used.” Damned right, it was never used; it wouldn’t START! I tried EVERYTHING. Nothing worked! After changing this, tweaking that, and pulling that cord until the tween of my fingers bled, I THREW THE THING HI-I-I-GH IN THE AIR! My wife said “Yeah; that’ll fix it! Great work, Tom…” Just for the hell of it, I gave the thing a pull. It started right up, and has worked right ever since! I don’t know what was more satisfying; hearing that engine run, or seeing the look on my wife’s face! Talk about a Hail Mary pass!

    Always have a spare spark plug handy. Spark plugs in 2-cycle engines die suddenly.

    Drain the fuel if you’re not going to use it for a while. On the small engines I pump the primer bulb until it sucks air, and then dump the last bit out of the tank. On the larger ones; outboards and the like, I run them dry, choking the engine as it starts to sputter to get the last bit out of the bowl.

  5. I believe the solution for a 2-stroke is a 4-stroke. Husqvarna makes one that looks very much like the picture, but it does suck, squeeze, bang, blow. Had it for five years, treat it like I hate it, never service it, kick it out of my way all winter. The fuel tank is stained dark brown from varnish. Starts within three pulls every-single-time.

    1. I tried going the 4-cycle route. ‘Made sense; no mixing oil; no worrying that my wife would put straight gas in the tank and destroy the tool. It was a weedeater. I had a hedge trimmer attachment for it. When you use the hedge trimmer attachment the engine can be held vertical or even upside down. When you do this with a 4-cycle, the engine smokes like hell. It was useless. I went back to the 2-cycle…

  6. Biggest way to increase the life and reliability of chainsaws, mowers, blowers and whackers is to let them warm up a good bit before applying full power. Failure to do this often lead to “cold seizures.”

    What happens, is a cold chain saw is started and then almost immediately is pushed to full power cutting a log. The piston has far less thermal mass than the cylinder and will heat up much faster under the sudden full power.

    The piston consequently expands faster than the cylinder and the clearances between the two reduce. This causes much accelerated wear on the piston, rings and cylinder and can trash the engine quite prematurely.

    Always allow a cold engine to gently warm up to full operating temperatures before applying full load/power.

  7. For those who can’t find ethanol free gas it is possible to remove the ethanol yourself. A bit counter intuitive, but you add a full measure of water to the gas, agitate it, let it settle, drain off the bottom. There are a number of videos on the web. Works very well.

    1. Yes, you can remove the ethanol with water and then separate them. However, and this is a biggie, you will significantly drop the octane level of the fuel. Ethanol is used in large part to boost the octane rating. Fuel with too low of an octane rating for a given engine can cause pre-ignition, often called “knock” due to the sound. This generally reduces engine power and over time will prematurely wear or damage the engine.

      What is pre-ignition? Air and fuel are mixed together in the carburetor or the fuel infection system and that mixture goes into the engine cylinder. The piston moves from is lowest position up compressing the mixture. When the piston is near it highest position in the engine cycle, the spark plug ignites the mixture which burns rapidly creating more pressure pushing the piston down and turning the crankshaft. However, when gases are compressed they get hot. If the mixture gets hot enough, it can spontaneously ignite on it’s own before the spark plug fires. That Is pre-ignition and means it’s creating pressure before the piston got to its highest position and is now pushing on the pistons too soon. Octane defines how much the fuel can be compressed before pre-ignition occurs. “High compression” engines need higher octane but are more efficient and can produce more power. However, there is no benefit or increased power by using higher octane fuel in a lower compression engine.

      If 87 is what the engine was designed to handle then using 89 or 91 don’t do anything that the 87 couldn’t achieve, which is preventing pre-ignition. That’s it. There is no more power or fuel efficiency as the BTU content of higher octane gas is essentially the same and the thermodynamic efficiency of the engine isn’t changed by octane. So using 91 in an engine designed for 87 or 89 is just wasting money.

      Many of the issues with ethanol fuel arise when it absorbs water. Keep it well sealed from the ambient air.

      (Oh, my day job is an engineer and I have worked for a major engine manufacturer for over 20 years, most of it in engine controls and diagnostics for many diesel and a couple spark engines.)

  8. Reply to Bill:
    Many thanks for your input from this end-user. I do let my tools warm up prior to actual use. The nice thing about the small, light 2 cycle engines is that warm up does not take long at all. ( on order of several minutes.) I did not mention allowing time to warm up because I usually take that time to size up the job, decide where my first cut on a tree or log will take place (to avoid a pinched saw bar). Years ago when I moved into my new home, I made the switch to electric power tools for several reasons: less thought involved in using the tool itself and avoiding the smell of gas, gas/oil mix within my garage.
    Many of the jobs I did were relatively small around yards of homes in suburbs. For such jobs, I rarely used a gallon of saw-gas mix. For such small jobs around suburbs, I carried small amounts of saw-gas mix in a Sigg fuel container. These are/were available at REI and other mountaineering stores. They were designed to carry and store white gas. These are great containers because they are small, light and easy to work with for those jobs that use 1 tank of fuel or less in 2-cycle applications. Just remember to use hang tags on the bottles to avoid mistakes or confusion.

    1. I really like your idea of Sigg or MSR backpacking style fuel bottles. The best part is put fuel in them, screw the cap on tight and the fuel is well sealed inside. A good sealed container is the best method of storing and keeping gas fresh as it traps and retains the more volatile hydrocarbons that otherwise would evaporate away and keeps moisture out and the fuel dry. Vented fuel tanks are the Worst for gas storage.

  9. Tmac: : “Purchasing a used power tool at a garage sale” Danger! Danger!
    Nobody sells a motor vehicle or a used power tool because they run too well.
    I am glad that drop-kicking that bad boy worked for you.

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