What is the gas/oil mixture for the Toro Model 20684 and I need to locate a manual for the model if possible.

Your recycler mower is either gas or electric (as you may know). The gas models use straight gasoline. You do not mix oil with the fuel.

It depends, Toro made 2 cycle and 4 cycle Mowers......Look and see if there is a oil dipstick,If so it is a 4cycle , If no dipstick or plug at crankcase to check oil then it's a 2 cycle

The manual can be downloaded from this webpage, you need the serial number to do this.

https://lookup3.toro.com/request/request.cfm?lang=uk_en

Two stroke engines usually use a 1:50 oil/gas mixture but it would be wise to consult the manual.

Hope this helps !

Put SAE 30W oil in it and do not mix with gas.

I assume you me It required an oil/gas mixture and was run on straight gas. Depending on how long it was run with no oil, It is very possible that the piston walls are scored or some other form of major damage was done. If it stalled after running with straight gas for a while this is probably what happened. Just try starting it with fresh gas/oil mix as called for, Then go through and make sure it is not flodded and the spark plug is clean.

The carburetor needs to be removed and inspected. The malfunctions possibly indicate the need for a repair kit. I've been unable to locate your exact model, but if it has the 2-Stroke engine (gas/oil mix), then you will at the very least..need a gasket and diaghragm kit installed per inspection. There is the possibility that the carburetor needs a complete rebuild and would require the complete rebuild kit. Remove the gas lines (after draining gas). Remove the carb and inspect the screws and tightness of the screws in the 2 end covers. Are the screws tight? If not tighten them up and reinstall, trying to restart the machine. Post back if needed.

50:1 petrol/oil

The proper mix is 50:1. The link to the manual is
http://ourfamilys.deandrea.net/BobKitty/User%20Guides/tosnowss.pdf

The fuel mixtures can be found on page 11. Hope this helps.

if you changed the oil recently you need to use SAE30 and not 10w30. Causes pressure buildup.

sounds like it is "hunting". it is a fuel mixture issue.