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Discussion Starter #1
Hi!

I have some minicars of the 50s and 60s that have two stroke engines and here is my question:

if the factory recommended gas/oil ratio was for a given engine was -say- 20:1 when the engines was newer " and using the the contemporary 2 stroke oils then what would the ratio be today for the same engine but using (obviously) today's 2 stroke oils?
Would the ratio change (that is less oils porcentage) on account of newer, more developed oils?
Or would there be no change?

I ask because when using the factoray recommended ratio my engines smoke more than usual, so I assume maybe the ratio should be modified (??).

Can anyone help me on this one?

Thanks,
Lars
 

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Hello Lars; I asked a similar question not long ago no good answers. Everyone has their own special system, right or wrong. The main thing is to find a clean burning combination, now days the PV plugs & performance sufferers.
 

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Go with what the maker of the oil tells you. The additives in the oil have a lot to do with the recommended ratio, and if you run some of the modern oils at a real rich ratio, you can have problems from certain of those additives.

The manufacturers of the old 2-stroke cars, bikes, outboards, garden tools, etc., were quite aware of the peculiarities of their widely varied buyers. They didn't know if a machine would be sold to a mechanically-aware westerner or some foreign native with little understanding, with nothing to use as premix or injected oil but automotive motor oil, and with an attitude that if the machine failed to work, it was the will of Allah in any case. So the manufacturers, in many cases, would recommend a conservatively rich premix ratio, one that was okay with the old oils (or with 30wt motor oil), but is not okay with new oils.

Not only clueless foreigners were a problem for manufacturers. Old guys like my own dear dad, who had grown up poor and frugal in the depression of the 1930s learned to fix their own equipment on the cheap. In succeeding decades, these fellows often had/have the idea that the "newer and better" products, maybe including 2-stroke oils, were a marketing scam intended to make them pay extra. I worked in a small engine shop one year, and we would sometimes get these guys' chainsaws and weedeaters and mowers to fix, so loaded with deposited and burned-on carbon and crud that they'd hardly turn over. We referred to their choice of cheap motor oil for premixing as "Bunker C."

Don't be confused by the very oil-rich ratios used in many kinds of racing. Those are for different oils and different conditions.

Confusion arises today from the malign influence of the lawyers. The oil makers would rather put the liability on the engine manufacturer, and therefore often tell you to go with the manufacturer's recommendation. If the manufacturer of the old engine had anything to say today, he would possibly also want to shift the liability away from himself.

The oil maker knows how his product is formulated; the manufacturer, all those years ago, had no way of knowing about today's oils (or about today's fuel, gasohol). Go with the oil supplier. You can use his conservative ratio, if you like.


(A very strong suggestion: on any old motorized equipment or vehicle, take out the fuel tank and get all the goop and rust cleaned out of it via steam-cleaning or hot-tanking. If you don't, gasohol will loosen up the rusty glop and send it through your engine, EVEN THROUGH A BRAND NEW FUEL FILTER, as I can personally attest. Clean the tank, treat it with a rust-converter, and the gasohol will keep it clean. Do the same with any hard lines, and replace all the soft lines, and the filter. Be aware that the fuel pump and carb in your old machine might have soft parts that gasohol might degrade; sometimes there are gasohol-resistant replacement parts.)
 

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Discussion Starter #4
Many thanks to John Tice and also to Seattle Smitty for all the funny as well as useful comments.
I am not sure what to conclude but I guess I will get the fuel tank & lines cleaned and lower the mixture ratio a bit (less oil).

I am sorry for not replying before, I was away.

Thanks again.
Lars
 
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