Why two different mixes? Easy; it depends on the quality of the oil you use in the mix. If you�re using high quality oil, like Shindaiwa or Echo two stroke oil, it's recommended you run the mix at a 50:1 ratio. Some of the higher quality oils will also have built in fuel stabilizers and smoke reduction formulas etc. This will vary between suppliers. If you�re using another brand of oil or one of lesser quality it's recommended you run the mix at a 25:1 ratio.
The ratios:
50:1 = 100ml of two stroke oil to 5 litres of unleaded petrol
25:1 = 200ml of two stroke oil to 5 litres of unleaded petrol
This is incorrect and very bad information. Quality of the oil is irrelavant. It should meet the certain standards and say so on the bottle.
I use the valvoline 2 stroke oil that my local go-lo sells for $6 a litre, it seems to do the job. I do mix my fuels a little richer as normally I am starting engines that have sat for many years and may have dry bearings.
This might sound like a good idea but it is not.
With the dry bearings. Best thing is to remove the plug, tip the mower up on its side wind the piston to the bottom and pour a small amount of oil in, it will flow to the crankcase via the transfer ports.
With Premixed fuel you are adding oil to the fuel and this takes up volume in the fuel. The jetting is set to account for the percentage of flow through the jet that is combustable fuel plus the non combustable oil. If you alter the ratio you are infact changing the jetting as more oil means less fuel and vice versa.
By adding extra oil you are making the engine run leaner. This could cause any number of issues and will decrease engine life.
By adding less oil you are making it run richer. Generally oil starvation will not be an issue but you could have issues with that black splooge stuff as the combustion tempratures will be down. Could also get carbon build up. It will smoke more as the combustion temps are not high enough to burn off the oil.
If you alter the premix ratio the jetting needs to be altered accordingly. Or engine 'tuned' if you like. This is OK on a motorbike or similar with a more complex adjustable carb, but on a victa with set jetting you should stick with the reccomended ratio.
Best thing to do is have fresh fuel.
Bob.
