Fuel Mixture Supporting evidence for 2-stroke oil/fuel ratio

Discussion in '2-Stroke Engines' started by Fabian, Oct 14, 2009.

  1. Fabian

    Fabian Well-Known Member

    G'day all

    Just a quick note for the banter going on about what oil/fuel ratio is best.
    I've written up some of my ideas on the best ratio for the issues we have to deal with on our 2-stroke Chinese Bicycle Motors.

    I firmly (and with good supporting evidence as listed in previous post) use plain old 2-stroke mineral at 20:1.

    Doing some research i came accross a castor oil fortified 2-stroke oil listing the oil/fuel ratios for various applications.
    In the world of lubrication, nothing gets any better than straight degummed, first pressing castor oil for maximum tolerance to heat and pressure.

    This product (similar to others) is a blend of castor and synthetic but when the going gets tough, it's the castor giving you the real protection.
    Scroll down to the bottom of the page and look at the oil/fuel specifications.
    Since our bicycle motors are air cooled and small capacity, they most closely fit the "Kart" specification.

    My goodness, they recomend 20:1 and that's with the extra protection of castor oil.

    Naturally, everyone will have their own opinion
    Still, it's food for thought before you try and run your Chinese Bicycle Engine engine on 40:1 or worse, a nightmarish 50:1 just because the oil container says it is recomended for use at 50:1


    Cheers Fabian

  2. Pablo

    Pablo Motored Bikes Sponsor

    But you offer no proof that the correct oil at 50:1 in a normally loaded MB engine does harm. (because it doesn't).

    I have nothing against Klotz - good stuff - but what about all the guys zipping around with 100:1? (And I am NOT just talking about Amsoil, Opti guys!) - however to use an advertisement as your backing (while stating this is the best oil with castor, etc) is no different than someone reading a bottle and saying "yep 50:1".

    I'm not posting to say 20:1 is bad or to say 100:1 is bad or 32:1 is bad.

    What I AM saying - use what works and a great starting place IS what the oil manufacturer recommends.

    BTW - I use Amsoil Racing oil (Dominator) with my own castor oil added. Not near as dirty as Benol. :jester:
  3. Fabian

    Fabian Well-Known Member

    Yes Paul

    You make a very good point: quote "But you offer no proof that the correct oil at 50:1 in a normally loaded MB engine does harm. (because it doesn't)."
    I am certainly not advocating one manufacturer of oil over another - just that they had a website listing recomended oil/fuel ratios with a castor fortified oil.
    I use mineral based 2-stroke oil at 20:1 with great results - when i used 25:1 the results were not so good.

    Using the SickBikeParts Jackshaft system the only throttle position the bike ever sees is 'Wide Open Throttle'.
    As soon as the bike hits 3500 rpm i change up a gear and run full throttle, change gear, run full throttle, change down a gear for a hill, run full throttle, maintaining the best speed i can squeeze out of the motor.
    With the trailer attached, i'm really squeezing the motor for all it can give.

    The bike never sees anything other than wide open throttle.

    I will agree that if you are just tootling around, hardly ever using wide open throttle, you can get away with leaner oil/fuel ratios.
    From my experience though, there is only one throttle position - Wide Open Throttle as you can't get enough power at any other throttle position, so i'm coming from a perspective where the engine never gets a rest; it runs hard from the moment it is warmed up till the trip is over, sometimes being a 3 hour trip with in situ refuel.

    I've posted plenty of supporting evidence in another thread and there's enough data if it needs to be researched and verified; a good education in 2-stroke lubrication and fueling requirements presents itself when involved in Karting where the top guys extract every last little drop of performance out of those 2-stroke engines and in the search for that little bit extra, sometimes experimenting with friction welding internal components.

    Last edited: Oct 14, 2009
  4. Pablo

    Pablo Motored Bikes Sponsor

    I was not talking about YOUR application. Pulling a trailer, up hill, at WOT - well 20:1 is fine. I thought I was fairly clear that I was speaking to a larger audience than just you.

    All I see is a link to Benol, and yes I have read all the 10:1, 15:1 "studies" - but those guys actually adjust their fuel/air mixes for conditions, include fuel/oil ratio. What other supporting evidence did you post? I'm not trying to be a wise guy. I can distinctly say every MB meet I have been to, there is a VAST difference between what those engines see and a racing kart engines see! Huge, really. Again - your application may even be WORSE than a kart, but recommending folks will automatically get better protection at 20:1 is a bit broad for my tastes.
  5. Fabian

    Fabian Well-Known Member

    You have a completely valid point Paul.

    I have no reason to disagree - your logic is sound based on variability of operating requirements that my application never gets to see.

    My experience though is that there's only one throttle position for these little Chinese engines - Wide Open Throttle, trying to squeeze on them everything you can get, whilst keeping the rpms less than 3500.
    To do that though, you need a Jackshaft Shift Kit.

  6. oldsalt

    oldsalt New Member

    Why would a mixture leaner in oil than, say, 36:1 be desirable? Unless of course it's a competition engine that needs to have its high octane fuel as unadultarated as possible. The oil seriously lowers the rating. Maybe for economy? But the math seems to say that a 50 cc engine operating 100 miles per month will save cents, not dollars, in operating cost. The only other reason I can think of is the plug fouling issue. But that's a red herring. Since the early '60s modern two cycle oil has vertually eliminated that problem. That was a problem back in the loop scavaged, baffled-piston days, but not now. BTW. I use 20 or 24:1 in every two cycle I own.
  7. Fabian

    Fabian Well-Known Member

    Exactly, oldsalt

    There is nothing desirable about lean oil/fuel ratios except for emissions reasons or trying to extract the last once of power out of a precission engineered liquid cooled 2-stroke racing engine.

    Over and over again, the issue of hydrodynamic piston ring seal through an oil barrier is widely overlooked, especially in an air cooled engine manufactured with poor engineering standards.

    It's got far less to do with engine protection and more to do with maintaining combustion presssure as the rings pass over areas of localised bore distortion caused by significant temperature variation and metalurgy that isn't the image of perfection.
    Having said that, oil absorbs heat and helps control temperature variation - running overly lean oil/fuel ratios robs you of this critical aspect regarding thermal stability in the cylinder bore area, especially on the exhaust side.

    These debates will contine - it's the nature of human emotion over riding logical analysis by science.

    Last edited: Oct 15, 2009
  8. Pablo

    Pablo Motored Bikes Sponsor

    I really can't argue with that logic.

    I won't even try to override science - BUT there is nothing WRONG with a street MB in a moderate climate with a 180# person with a standard engine running a good oil at 32:1 or somewhat leaner. He will see no excess wear, lose no power, etc......especially when everyone is trying to shut 2 strokes down for emissions.

    Use the ratio that is correct for your conditions! :detective::jester:
  9. Fabian

    Fabian Well-Known Member

    That's good logic Paul: quote "Use the ratio that is correct for your conditions!"

    I would never go against this reasoning - if you are just tootling around, in areas of pedestrian traffic, using maybe 1/4 throttle and never running periods of wide open throttle, 20:1 would not be of any advantage; just making excessive smoke and irritating people around you.

    I will say this though, using 20:1 in my application of constant wide open throttle, the engine never smokes when under load.
    It will however smoke somewhat when idling at a set of traffic lights and when taking off from traffic lights till the crankcase has been purged from settled oil, whilst idling at the lights.
    Typically, i time my way to a set of lights so the lights have gone green when i get there.

  10. motorpsycho

    motorpsycho Active Member

    why is it then, that my 2 stroke weedeater recomends 40:1, my 2 stroke chain saw recomends 40:1 and the instructions for my 2 stroke bicycle motor recomends 40:1(after break in)? every 2 stroke that i have ever dealt with says to run at 40:1. my father in laws 40 h.p. outboard also recomends 40:1.
    I have been running my weedeater at 40:1 for 15 years...maybe 40:1 was the suggested ratio at the time that it was made? my chain saw is about 8 years old...and i still run it at 40:1. My bike motor was built jan 2009, and it says right in the instructions to run it at 40:1 as well.
    A bunch of people say that 40:1 is too lean.
    so.....who's right and who's wrong?
  11. Fabian

    Fabian Well-Known Member

    Hi motorpsycho

    For your answer you need to look at emissions regulations.
    If the government stipulates an emissions regulation that works out to be 50:1, the manufacturers will all recomend 50:1

    Manufacturers must then use methods of giving the consumer reliability by new metals technology and cylinder plating technology and a further option of simply detuning their engines to give the required reliability.

    Nikasil plating technology came into widespread use when emissions regulations dictated the move to 40:1 oil/fuel ratios.
    Unfortunately our cheap and nasty Chinese Bicycle Engines use a very poor quality version of a chrome plated cylinder bore and the metal used in the casting process is also bottom of the barrel in respect to quality.

    You can still use lean oil/fuel ratios with a well designed cylinder structure made from high grade alloy and a laser etched chrome plated cylinder bore - naturally the price reflects the technology.

    At the end of the day, rather than asking the question "who is right, who is wrong", it's only a simple matter of spending 3 or 4 weeks doing some serious and intensive research to find a definitive answer - basically, start opening a lot of books, give yourself the opportunity to spend time in a large library researching the topic and use the internet for any out of date scientific publications.
    Military defence research papers are another good source of information as their requirements are not bound to civil emissions regulations - they need a product to work as well as it can.

    You have the power to fill your head with well researched knowledge - a little intellectual fortitude goes a long way to providing answers.

    Last edited: Oct 15, 2009
  12. arceeguy

    arceeguy Active Member

    FYI - Your typical Home Depot string trimmer or blower engine runs the piston in a plain aluminum bore with no hard plating, and they run 40:1 mix. The chrome plating in the bicycle engine (or steel cylinder liner in some models) is superior to those little engines.
  13. 210061741

    210061741 Guest

    I believe knowing your bike works the best.
    I run different oils at recommended mixes also with 2 to 4 oz per tank octane booster. 12$ a bottle the real deal.
    When the mix is lean it will run much diff then with rich.
    I mix mine right around 35:1.
    And i ride hard very hard.
    High rpm and fast with a 36t sprocket.

    I heard my bearings squeeling for a wile.
    Sprayed some Industrial lube in the intake and it went away.

    Can't wait to see what the inside of my motor looks like.
    I have abused it to the max for 3 mo.
  14. Fabian

    Fabian Well-Known Member

    Hi arceeguy

    Go down to home depot and find the contact number for the company selling those string trimmers.
    Call the company and ask for the technical department, ask them what plating process is used on the bore structure.
    Nikasil impregnated aluminium looks just like plain aluminium - it is possible they are using a Nikasil plated bore but it's not likely at very low prices, though i could be wrong.

    You get what you pay for but if steel rings are running on a non plated aluminium bore, you really get what you pay for - a case of buyer beware.

    A chainsaw can sell for $200 and you can buy a similar chainsaw for $700 from a reputable manufacturer selling their equipment to professionals - what could possibly be the difference apart from price.

  15. oldsalt

    oldsalt New Member

    The history of DOT and the EPA shows they will stipulate the craziest things; Sometimes things that are not possible at all, but, more often, things that are just silly or wastefull in the long run. If a person goes to a junk yard he will now see huge numbers of what look to be good, late model, lightly used lawnmowers. But the decision to allow up to 10% alcohol in our gas [without the necessity of declaring it at the pump] ruined untold millions of them. It's easier and usually cheaper to buy a new one than repair, and to **** with the eco impact. The alcohol is hydroscopic and ruins the carbs over the winter. Would mandating 40:1 oil mix be something that they would do without considering the consequences??? Sure they would, all the history clearly points to that. As far as I'm concerned they are quite welcome to use 50:1 in THEIR machines.
  16. arceeguy

    arceeguy Active Member

    I don't need to call them. You aren't getting a leaf blower with a nikasil, chrome or other hard plated bore for $99.

    Most consumer grade power equipment run their pistons in plain aluminum bores. (Briggs & Stratton Kool Bore) Even a cheap 2 stroke will last several years under normal consumer use, and aluminum bore 4 strokes can go for decades.

    People will debate 2 stroke oil ratios and what type of oil (like Castor/Dino/Synthetic) forever. Everyone is going to do what they are comfortable with.
  17. outrunner2

    outrunner2 New Member

    I've been using Amsoil Dominator synthetic oil at 40 or 50:1 ratio for over 5 years in all of my 2 stroke engines, which includes 11 RC airplane engines, 2 weedwackers,2 chainsaws, Ryobi 2 strokes, Husqvarna 2 strokes, Homelite 2 strokes and my MB China 2 stroke, without any oil related problems, or piston seizures. I run my MB full throttle EVERY time I ride it for short sustained periods. Upon tear downs of my MB engine and dozens of RC airplane engines that are rated somewhere between 1 hp to 16 hp, they look
    clean and golden colored throughout the upper and lower end. Not only am I the only one to have great results with synthetic oils (some with castor oil
    added for extreme heat stability), but at LEAST 35 to 40 of my fellow flying club members use synthetic oil at 50:1 and a few at 100:1 ratios, so the real proof is in the seeing and experiencing the actual results in person over several years! Our flying club is at gmarc.com if you would like to see the number and size of the aircraft that are flown daily when weather permits.
    Synthetic oil has thermal stability in extremely low or high temperatures to maintain lubrication and viscosity. Crude oil cannot compare to it, and will break down MUCH faster during thermal loading and extreme pressure demands.