Need help with gas/oil

Discussion in '2-Stroke Engines' started by Greendice34, Aug 7, 2015.

  1. Greendice34

    Greendice34 New Member

    im sure this has probably been asked a million times but I don't wanna go through and find it haha. So I just finished building my 2 stroke motorized bike and I don't know exactly what type of gas or oil to use. Right now I have a gallon of 87 gas and some 2 cycle oil and the things I read say to use synthetic oil and some say it doesn't matter? what kind of gas and oil should I be using if it actually matters?
    Here is a link of the oil I have right now:

  2. crassius

    crassius Well-Known Member

    you'll get a lot of opinions on this

    I used to use 16:1 for first gallon, then 32:1 thereafter with cheap walmart oil. With the newer motors we're getting now (if your seller gave you a new one rather than a pre-2012), I put maybe a quart or so of 16:1 in for getting it going, then add 32:1 thereafter as soon as it starts to run well.
  3. butre

    butre Well-Known Member

    I use 50:1 from the moment I first start it all the way until the engine reaches the end of it's service life. I usually tell people to run 32:1 to be safe though.
  4. KCvale

    KCvale Motorized Bicycle Vendor

    I run 25:1 (5.2oz 2/3 cup per gallon) non-synth for the first tank, then 32:1 (4oz 1/2cup per gallon) synthetic from then on.
  5. Fabian

    Fabian Well-Known Member

    I use the highest grade pump fuel, and the cheapest air-cooled specification 2-stroke oil at 25:1 - has served me very well.
  6. KCvale

    KCvale Motorized Bicycle Vendor

    Oil doesn't combust, only gas vapors do.
    All you are doing is 'watering down' your power with too much oil.

    All the oil is for is lubing the bottom end and not all the intake even goes to the bottom.
    The rest just fouls your plug, makes smoke, and drips out the tail pipe when you stop.

    32:1 is plenty safe, less oil if it's a good synthetic like 50 parts gas to 1 part oil.

    Octane does not combust either.
    It actually performs the opposite, it keeps the gas/air mixture from igniting too soon in high compression engines.
    These 2-stroke engines are far from high compression and little chance you will ever get a pre-detonation 'knock' as it's called unless you are running way to lean and hot.

    I use premium gas because it is usually cleaner (Less Ethanol) fuel, and it makes me smile when even the clean stuff is less than $2 for 70+ miles of operation.

    With most of these 2-stroke engines the bearings, cylinder walls and rings will wear out no matter how much oil you put in the mix as they are crap to begin with.

    So you can live with an underpowerd, smoking, oil dripping machine and get maybe get another 100 hours out of the engine, or just give it enough of the good stuff available these days and get a power boost, no smoke, and no drips of un-burnt oil when you park the thing.
  7. Fabian

    Fabian Well-Known Member

    In an air cooled engine, the oil is used as a heat mediator to carry away heat, and to quench hot spots.
    That is why it is so important, (especially with poor metalurgy of these engines) to use 25:1 but an equally important factor is the hydrodynamic barrier that the oil gives; helping to prevent blow-by as the bore shape distorts from a circular shape, due to poor metalurgy.

    In these engines, the oil content in the fuel actually increases power, even though the oil does not burn, and lowers the octane number.
  8. butre

    butre Well-Known Member

    how you ride makes the biggest difference in your oiling requirements. next time you have your jug off, dip into the crankcase and see how much oil is in the bottom. always full throttle heavy load, use more oil. full throttle light load, use less. always part throttle, use more oil
  9. bakaneko

    bakaneko Active Member

    I did 16-1 break in with premium castor synthetic oil, which was pricey. It did not smoke. I am running 25-35 after break in with cheap Menards 2-stroke oil, used for small motors and lawn equipment. It smokes a little but the price is great.

    Also, I know many want to really take care of their engine and get the best performance, but for others it is a cheap hobby or transport. Therefore, how much do you want to spend on oil for a $115 dollar motor kit... :confused:
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Actually, using high grade synthetic oil defeats the whole purpose of "breaking in".

    Breaking In is the process of letting the cylinder wall and rings wear so they end up matched well seated so they retain the most compression.
    Once they wear in just right is when you want to stop the wear.

    That's why you take it easy on power and use the basic lube property oils, and a lot of it, to get rid of the derbies and cool the process so the crucial ring/cylinder wall can wear in and be happy.

    Do it right and you feel a gradual increase in power due to better compression as they seal up.
    One tank of 25:1 is all I use, with a mix of easy riding and hard full throttle.
    After that, stop the wear and lower the oil in the gas to better the power.

    As for dissipating heat, umm, I shall remain nice and just say you adjust the heat range by the spark plug and not by the gas/oil mix in way shape or form.
  11. butre

    butre Well-Known Member

    easy on the power? no, full throttle heavy load all the time. never hold top speed for the first 5 miles
  12. sbest

    sbest Active Member

    I do not know for these engine, but I have thousands of kms of experience riding my 2000 KTM 125 EXC in dirt and on the highway.
    I have tuned the 125 engine to run on 87 octane, I might have lost one or two HP, but worth it to run on any fuel I can find. With the highway tire and sprocket pictured below it has a top speed of 140 kph (87mph) and can do any highway grade at 110 kph (68mph) although I tend to keep it to 100 kph because of the rpm. My point is, I am very familiar with putting huge miles and high speeds on a small 2 stroke engine.


    This bike had 40:1 synthetic oil for the first year of its life and 50:1 thereafter. I ran most of a tank of 100:1 through it one weekend. Bonehead math error. No bad effects. I have had 2 engine failures in the 15 years I have owned this bike. At 7 years I dunked the bike, completely, in muddy water. Broke rings, drove it home with no rings. Had to push start and it wouldn't idle but it made it 15 kms to the trailhead with zero compression. You cannot kickstart, it is a push down a hill sort of thing. Actually I dunked it annually at the same event 2 more times before I finally needed a new crank and cylinder. The other failure was a forged piston that was not allowed to warm up properly. Gave it full throttle after only a 1 km warm up and it locked up and set me on my butt. Or rather wore the skin off my butt. My point? 15 years and many thousand kms at 50:1 and no oil related failures.

    The head on the right was my high mileage 50:1 lean jetting head:

    Note the differences in combustion chamber shapes. The one on the right (and middle) is a mid-range torquer.
    The one on the left is a high rpm screamer. Oh yeah, my point? Less oil is better.

  13. HeadSmess

    HeadSmess Well-Known Member

    oil? pffft. the finest swiss butter, if you will. made with real swiss cow cream, educated in geneva and trained in all the fine arts. the cow AND the cream that is.

    all mellowed with some overproof motor spirit imported from the far middle east, blended with virgin first pressing castoroil and menthol for that refreshing aroma we all know and love :)

    the exact specific formulae remains a family secret, closely guarded from the fiercest of rivals.
  14. butre

    butre Well-Known Member

    My family recipe is avgas and whatever cheap oil the oreilleys or autozone carries mixed at 50:1. usually that stuff that says low smoke on the bottle but really smokes like a steam engine
  15. sbest

    sbest Active Member

    From experience, I usually go the other way around. I build the engine to use the available pump gas and use the best oil I can find.

    Fuel, you use a lot of and are often forced to use what the pump has. Build the engine for it.
    Oil, you use a little of it and is critical to the long term health of the engine. Better oil is cleaner, lubricates better, and MOST importantly, less prone to fouling the plug.
    If, perchance, you cannot find good oil at a backwoods gas-stop, one tank of cheap oil will not kill your engine.
    One tank of 87 octane fuel will kill an engine built for 100 avgas.

    $12 for a litre of good synthetic oil figures out to 72 cents in a tank of fuel.
    Cheap oil is a poor way to save 54 cents, especially if you are doubling up on it to "stay safe".

  16. HeadSmess

    HeadSmess Well-Known Member


    hmmmph! :mad::mad:
    steam ENGINES do NOT SMOKE!!!!

    the dirty coal fired boilers DO! :p

  17. butre

    butre Well-Known Member

    avgas isn't too hard to come across around here, and I always keep a few gallons spare. avgas is still leaded, if you've ever used leaded gas you know what kind of lubricity benefits it has compared to unleaded gasoline. remember when unleaded gasoline first came around and everything that was already on the road needed the valves lapped every couple of years? that's because the tetraethyllead in leaded gasoline kept the unhardened mild steel valves from wearing down.

    I don't use avgas for the octane rating, I use it for the TEL. my bike will happily run on 93 octane if I throw a splash of xylene in there
    Last edited: Dec 23, 2015