As long as the oil sump is filled to the correct level with engine oil, running it on 2 stroke mix will only cause a lot of smoke, a fouled spark plug, a clogged muffler and crudded up valves that stop sealing after a fairly short time. Since a 2 stroke has most of those faults routinely, it isn't a big problem putting 2 stroke mix in a 4 stroke for a short time until you get it straightened out. What is really important, is ensuring that the oil sump is filled with 4 stroke engine oil. Most people who put 2 stroke mix in their 4 strokes neglect to put oil in the sump, and that ends badly.
