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  • 2 Cycle Engine Mix Ratios

    So what part of a 2 cycle engine determines what ratio to use? I have chain saws that range from 16:1 to 50:1. Weedeaters from 32:1 to 50:1. What's the deal? Would a 16 mix motor lock up if fed 32 mix? It sure would be easy to have one mix fits all......

  • #2
    It probably depends more on the oil you are using. Some synthetic oils can be run at up to 80-100:1 ratios. On the motocross bikes i ran long ago i finally stuck with 36:1 for most mixes. There are a lot of considerations to be made also. Higher rpm motors will last longer with a richer mixture, say 28:1, and lower rpm motors will like a leaner mixture, say 40:1.

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    • #3
      2 cycle engines tend to wear out very fast I think it is because of low lubercation. I do not use recommended oil mixture I mix it caster 10% oil with 90% gasoline. I buy caster oil at Farm Supply or Horse Supply stores $12 per gallon. Caster oil does not fowl out the plug and does not smoke much because it will hardly burn all it does is provide excellent lubercation. I have some 2 cycle engines that are 30 years old and still run good.
      Last edited by gary350; 08-22-2010, 05:22 PM.

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      • #4
        It works like this..... Bushing motor gets approx 32:1
        A motor with a needle bearing on the big end gets approx 40:1
        A motor with needle bearings on the big and small end gets 50:1
        Then there is the synthetics which are supposed to be slippier and the molecules are all the same size, yada yada.. I know for a fact that you develope the most horsepower with 32:1. If you want to race and rebuild the engine every race run 100:1 syn... I personally run 32:1 dynosaur oil in everything... NEVER PROBLEMS + rings last forever.

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        • #5
          Originally posted by rws
          So what part of a 2 cycle engine determines what ratio to use? I have chain saws that range from 16:1 to 50:1. Weedeaters from 32:1 to 50:1. What's the deal? Would a 16 mix motor lock up if fed 32 mix? It sure would be easy to have one mix fits all......
          My cheap Homelife chainsaw says to use 16:1 mix and my Jap string says 32:1, I mix about 20:1 or so and use it in both, been doing it for years and never had a problem. The chainsaw smokes a bit but who cares as long as the plug doesn't foul. I've used several brand oils, can't remember the manufacturer but what ever they have on the shelf at the local farm store.

          JL................

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          • #6
            Opti-2

            I have been using Opti-2 smokeless in everything. It sure beats having three different cans of mix. I ran it in my Homelite EZ chainsaw that used 16 to 1. Other than adjusting the carburetor it worked fine. This is not an endorsement for others but I haven't had any problems. Jan

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            • #7
              The quality of the lubricant is of course the major variable in the decision as to what ratio of oil an engine manufacturer specifies.
              If he is confident in the design and material choice of components in his design he will specify a leaner oil ratio. If he is confident in his engine but suspects his engine is targeted towards a clientel that will use whatever oil is available, including 4 cycle engine oil, he'll recommend a more conservative, richer oil/fuel mix.

              Everything 2 cycle on my yard including weed eaters, chainsaws, bikes, etc. are all quality engines that utilize fully rollerized designs. So since the late 70's I've been using BelRay synthetic oil in everything, mixed at 50:1.
              No smoke, no fouled plugs, no problems whatsoever. Some of these have been worked hard, and although they are getting old they aren't tired yet.

              Outboard motors of course use a TCW spec oil so they have their own diet.
              Home, down in the valley behind the Red Angus
              Bad Decisions Make Good Stories​

              Location: British Columbia

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              • #8
                i run pretty much everything 50:1 except for the gentec genny i had i ran it 16 or 32 :1 as the 50:1 reccomend mix was a problem for it ,,

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                • #9
                  I have 3 stihl chain saws. I have only ran stihl brand oil mixed at 50:1. Oldest saw is over 28 years old and runs great.

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                  • #10
                    My Ryobi brush cutter runs 40:1 fully synthetic.

                    My Gilera CX producing 30bhp from 125cc (28,000Km on the engine so far) runs fully synthetic 'race' oil with the mix determined by the variable oil pump.
                    Paul Compton
                    www.morini-mania.co.uk
                    http://www.youtube.com/user/EVguru

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                    • #11
                      When I used to ride a 2 stroke dirt bike (Yamaha recommended 32:1) I went with a synthetic (Klotz) at 50:1. I never had a problem with lubrication or excessive wear. Being as I had a container of 50:1 mixed up I use if for all of my other 2 cycle implements.
                      I remember reading an article in one of the dirt bike magazines about dyno testing an engine on different oil mixes and they found that running more oil (to a point) worked better than less oil.
                      The one thing that has to be kept in mind when changing oil/fuel ratios is that the carb needs to be readjusted for the new mixture. When running less oil you are in fact richening up the mixture and therefore need to make adjustments. On some new 2 stroke carbs they have preset jetting and I would recommend using the manufacturers mixture amounts for optimal performance.
                      gbritnell

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                      • #12
                        A two cycle engine won't run on any type fuel...

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                        • #13
                          +1 for Opti 2. My Dad has been using it for quite some time in chain saws that require different mixtures. He's had zero problems and his saws get heavy use. Initially I was a bit concerned but after my Dad's experience and speaking to a fellow at a commercial lawn equipment service company and hearing his endorsement I was convinced that it was worth a try. Believe it or not, all of my equipment runs better and seems to be more powerful. It's also nice not having two or three different mixtures to worry about.

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                          • #14
                            Thanks! I had heard about performance and oil ratio. A friend bought a Husky chainsaw and they told him if he ran 40, it would last longer but if he ran 50, it would run GREAT! I can see a little change not being much of a problem, but when you talk about those 16:1 engines and putting something like 32:1 in it, that's half the oil. Perhaps the synthetics can make up the difference.

                            My old 16:1 saw sure does smoke........

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                            • #15
                              Another vote for Opti-2.
                              I too was turned on to it by a commercial equipment sales & service place ( service center for Stihl, Toro, and other such names). It works wonderfully in everything, and eliminates the hassle of keeping separate mixes on hand.
                              Lynn (Huntsville, AL)

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