Two Stroke Oil Ratio Question

hobbyheater Posted By hobbyheater, Sep 9, 2013 at 11:39 AM

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  1. hobbyheater

    hobbyheater
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    I inherited this small saw , its is mid 70,s vintage . Using Stihl two stroke motor oil what would be the correct oil to gas ratio ? 40/1 , 50/1 ? To be on the safe side I have been running 40/1 but it really smokes !
     
  2. clemsonfor

    clemsonfor
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    Most saws regardless of what they originally were are fine running on modern oil at 50:1 but 40:1 is fine. I bet that saw was designed for 32:1 with sae30 oil.

    It smokes cause the Carb is not adjusted right or air filter is dirty, or low compression.
     
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  3. MasterMech

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    The smoke is likely because bar oil is getting into the crankcase via the check valve. Common on vintage saws.

    Run the same mix you run in everything else. Follow the mixing instructions on the oil container. For what you have in the picture there that would be 50:1.
     
  4. MasterMech

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    I bet it was designed for 16:1 on 30wt. ;)
     
  5. charly

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    I love the wooden starter handle.. I use to use one or two of those for my climbing saws when I first started out... I found them to be cold blooded as moving around in the tree and setting up for another cut , the saw would need to be choked again.. Hated it,,, and also was an unreliable starter...I think they had weak coils!
     
  6. clemsonfor

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    I was thinking it as well butt thought it was newer than that.
     
  7. MasterMech

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    Well, maybe both Clemson and I were both right. It specs 32:1 but only with Homelite mix oil. Most saws of the time would spec one ratio with that mfgs oil and double the oil with anything else.
     
  8. charly

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    I would bet 40:1 full synthetic and you'll be fine! Can always check the plug after running it through some wood and shutting it off before it has a chance to idle.. Run some seafoam in with the mix, that will clean the internals as well..
     
  9. charly

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    I can remember years back have my metal gas cans with yellow paint on each saying, 16:1 and 32:1....wow I'm old !!!
     
  10. MasterMech

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    My SL9 has been pretty happy on 80:1+ ;)
     
  11. clemsonfor

    clemsonfor
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    I remember even my 390 said to double the oil if using anything other than stihl oil
     
  12. MasterMech

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    Really? I didn't think that carried into saws that recent.
     
  13. clemsonfor

    clemsonfor
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    Yep. I'll have to look for my book. But at that point it was o e of my largest purchases ever other than vehicles. That was like 04? And first piece of equipment, and I wanted to make sure I was doing everything right. Have no idea where the book is but I'll try and find it.
     
  14. charly

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    Have a friend that flys a backpack paramotor 2 stroke,, a real Guru on the Top 80 engines , 80cc... He rebuilds them, etc.. His motor runs Amsoil Saber @ 40:1 ix premium fuel, his unit is 7 years old with over 560 hrs, original ring , piston, etc.. Guys usually pulled the heads and put piston and rings in about every 100 hours... So that says lots about the Saber oil! Also he found the Avgas 101LL carbons the ring groove up, and causes a seized piston.. He said pump gas is the way to go... Now I know why my 12 year old stihl which has cut over 120 cords still runs great! He runs premium pump gas as well.. I just read some where's that mixing oil with gas as in 2 strokes lowers the octane rating.. So premium it is..
     
  15. TreePointer

    TreePointer
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    I run Stilh Ultra at 50:1 with 92/93 octane pump gas (<10% ethanol) in my old 2-cycle engines that specified as high as 20:1 in their old manuals. No problems and the engines and mufflers are cleaner than ever.
     
  16. charly

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    That's what I saw in my Stihl running Saber Amsoil after 5 years, clean spark arrestor screen and clean piston top, nice looking rings and no piston skirt scuffing.. That said it all for me, seeing is believing ...Plus I ran seafoam in my fuel..
     
  17. KarlP

    KarlP
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    Frankly I run all of my air cooled 2-strokes at 43:1 because 3oz per gallon is really easy to add & measure. It seems to work.
     
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  18. clemsonfor

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    Seems like a smart move. If I did not have a premix bottle for the boat I would do something like this.
     
  19. Pdesjr

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    40:1 with newer oils and premium fuel. I have 2 stroke equipment that is 30yrs old and still running
     
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  20. Bigg_Redd

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    This.
     
  21. Bigg_Redd

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    No it doesn't
     
  22. BrotherBart

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    Two stroke aviation engine maker disagrees with ya.

    "Aviation Fuels

    It is possible but not recommended to use 100LL AVGAS, since the the lead content will increase deposits in the combustion chamber and on crankshaft ball bearings, inducing premature wear. Its higher octane rating does not bring any significant advantage to the engine's operation"

    Feeding your Rotax 2-Stroke Aircraft Engine

    http://www.rotaxservice.com/rotax_tips/rotax_feed2.htm

     
  23. Bigg_Redd

    Bigg_Redd
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    So which is it? Does it "groove up" the rings with lead or with carbon?
     
  24. charly

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    Have a friend that runs Miniplane Top 80 Powerparagliding motors, rebuilds them for people.. He has saw first hand that 100% that 100LL sticks the rings on the motors, pushes the piston to one side and seized.. He can tell when someone ran 100LL just looking at things as they come apart without them telling him what they ran... 100 LL is not 100 octane rating like everyone thinks.. I read a post on the PPG group that it's not rated like auto fuel.. That's why they sell a decarbonizing fuel additive for 100LL..because of build up, which can cause detonation, etc. It was really designed for low compression, low RPM motors.
     
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