Fuel ratio

The instruction book for my unnamed 49cc two-stroke kit specified 16:1 at first and then 20:1 forever after. The result was that the thing barely ran, so I raised the ratio somewhat--probably to around twenty-something to 1, and it's happier.

M Kinsler
 
Thanks. I have three 2-stroke engines at the moment: the Chinese motorbike, a Weed Eater grass trimmer, and an ancient Lawn-Boy rotary lawnmower (with a magnesium chassis!) All have different (and somewhat vague) oil requirements.

Mark Kinsler
 
I'm surprised at this, for synthetic oil burns with as much enthusiasm as petroleum-based oil. I've used synthetic two-stroke oil occasionally since it was introduced maybe 45 years ago (it came in big cans made of paper with steel ends) and I never noticed any difference.
 
Yes I did read that before, but I hadn't quite thought about it when regarding 2 strokes, it's actually more ideal to burn away what isn't needed anymore, especially if it can add a bit of fuel to the fire during this part of the burn cycle, the underside of the piston and therefor cylinder walls are already coated in oil, more oil isn't really needed if it is good enough to lubricate while cool.

Not burning actually leaves stored energy behind in the form of heat and pollutants mixed in oil that just sticks to the road and everything else on the bike.. By the time the compression cycle begins there's already fresh oil on the cylinder, being that it shouldn't matter if the oil burned off during the power cycle, it's instantaneously refreshed with new oil anyway.

The design of these 2 strokes take care of themselves by adding fresh oil at every stage of the full cycle, so having oil that doesn't burn and sticks around results in needing less oil when using synthetics (per ratio to gas) since oil's going to be there still while new stuff gets applied. But it still doesn't mean that the 2 stroke can't endorse more power just by burning its own oil, the new oil comes in at exactly the right time anyway so hoping it sticks around for later doesn't mean anything.

Now 4 strokes.. Well you can change the oil as often as you want (like at the rate of 6 thousand times a second, if you wanted) but if there ISN'T any oil when you first run the starter then expect time to kill the machine. Synthetics help by sticking around longer to provide some lubrication during those "dry" cycles after letting it sit for a while. Mystery oil is a nice additive, it leaves a good oily film in the cylinders and helps to honeycomb the oil in the piston rings so there's more there to provide lube when starting.

Again extremely distinct needs between 4 and 2 strokes. One is much more prone to being run without proper lubricant on the moving and frictional parts just because oil isn't there at every given moment the motor starts to cycle. Simply put all your experimentation agrees totally on your prescribed use of oil type, even down to having more power, completely explained with simple stoichiometry that is key to understanding raw power availability behind the chemistry going on here.

If this was tldr: go to hell but understand that non-synthetics burn better in 2 strokes resulting in more power, 2 stroke design does not require oil be left behind for ideal lubrication.
 
I run my stock motor on 25:1 in my 12 degree (Celsius) weather down in Melbourne. Spark plug is perfect color, usually run the same during summer as well, better to be safe then sorry.
 
I've studied the subject a lot and I think it may very well be possible that the best protection for 2 strokes without exhaust power valves is with mineral oil. The highest quality mineral oil is called group 3 oil and it is allowed legally to be called synthetic because it is as good.
These oils use it:
Spectro Oils 2T
Golden Spectro Motorcycle Pre-mix
Amalie SynPlus Oil
Motul Scooter Expert 2T
Motul 510 2T

I am switching to Motul 510 (at 25:1) to see if my rings last longer (on my Suzuki 100cc) than with Motul 800 synthetic (45:1).
 
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I just found out that Yamalube 2R is made of group 3 oil and everyone highly recommends it
 
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