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2 cycle engine running problems

Discussion in 'Non-Mopar Tech Support' started by AllanC, Jun 20, 2017.

  1. NYBo

    Level III Supporter

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    I gave up on 2-stroke trimmers and got a rechargeable electric.
     
  2. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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  3. B10alia

    B10alia Well-Known Member

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    Probably lean running. I always jet my two-strokes a bit rich, from what I understand, the plug should be darker than it would be on a 4-stroke. Two strokes "gain" a lot of power when they run lean, i.e. the engine runs faster, but with less and less power as the mixture leans out. This adjustment is much more critical than on a four stroke since your oil supply is tied to your gas supply.

    You could try honing the jug to knock any glaze off and put new ring(s) in it, two strokes can be surprisingly resilient. I've heard of many moped engines which have seized and been recovered.
     
    AC TC likes this.
  4. AC TC

    AC TC Well-Known Member

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    - Always adjust the carb so its slightly missing at full throttle/ no load. ( fourstroking ) as he wrote, a lean running two stroke will sieze but itll run very good until it does.
    - you cant combat this with higher oilmixes...well, you can in a way if you go so far that it doesent run well.
    - they usually siezes at the exhaust side.
    - its not the lack of oil that makes it sieze, its the elevated temperature at the exhaust port thats damaging the piston. ( just like exhaust valves on a four stroke, but way more sensitive.)
     
  5. AllanC

    AllanC Well-Known Member

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    So a lean air fuel mixture causes an engine to run hotter??? That seems strange as more ambient air would tend to have a cooling effect on the combustion chamber which would mean the engine runs cooler???
     
  6. LouJC

    LouJC Active Member

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    With the 2 stroke it's the fuel and 2 stroke oil mix that cools the combustion process. I have a bunch of 2 stroke machines:
    1998 Toro 3000 GTS 2 stroke snow blower
    2005 Echo Leaf Blower
    2005 Echo string trimmer
    2008 Echo hedge trimmer

    Of the 4 of them I've cleaned out the carb on the Toro 2x over the years and replaced it 2 seasons ago because it developed thrittle shaft wear which caused uncontrolled revving. After that much better (Suzuki 47p 2 stroke basiclly bulletproof)
    On the Echos I had to clean out the carb on the leaf blower once and replace the ig coil once. That's it the others have needed nothing. I use the best Syn 2 stroke oil I can find and marine stabil. All we have here in Southern NY is e10. They all start well, the Toro usually on the 1st or 2nd pull, the others on the third or fourth. These machines get used a lot because we do most of our own landscaping and snow removal.
    I also have a 30 year old MTD push mower with a 3.5 Briggs, and Briggs powered lawn vacuum, pressure washer and emergency generator (125 hrs during Sandy)...
    2 stroke carbs like the one shown can be taken apart sprayed with carb cleaner and then blow out the passages. Many you tube vids on this....(see '65 Fords Channel or DonnyBoy both excellent)....
     
  7. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Lean operation always causes hotter temperatures. Fuel burns faster and hotter in the presence of more oxygen. It's raw fuel that cools the combustion chambers.
     
    Doug D and dana44 like this.
  8. B10alia

    B10alia Well-Known Member

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    Right, most of your cooling comes from the incoming fuel mixture. The lean burn is also a fair bit hotter than a rich burn. Combine these factors together and you get a charge generating more heat and with the engine getting less oil per piston stroke than it should be (even if your fuel:eek:il ratio is spot on, if the fuel/oil: air ratio is off, you're losing quite a bit of oil for any given operating condition).

    The other thing that I would note is (and I think others have mentioned this) two-stroke gas does separate over time. The lighter molecules (i.e. fuel) will naturally separate from the heavier ones (oil) over time. This could result in some of oil, along with some components of the gas, consolidating into an insoluble blob at the bottom of the gas can, given a long time. Even if the fuel is chemically stabilized, it's not necessarily mechanically stabilized. This means the first pour you get off of a can of old two-stroke gas could be mostly fuel, and 50:1 factory spec doesn't give you a whole lot of room to play with on the ratio. I try not to use any two-stroke gas that's older than a month or two, and if I do have to use an "old" can, I give it a good shake to blend everything back together as best I can.
     

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