Flypast,
First, a question... You cite the John Deere starting ether as 80% ether and 20% alcohol. Past discussions of JD ether saw no specific name for the "other" 20%, but there IS some form of propellant in the product. I suspect that 'other' 20% on the label is propane, butane or other flammable gas (at our usual temperatures.) It thus serves propellant and an easily flammable portion to aid starting.
Related thought - the JD can is labeled in ounces, apparently describing weight, as measures by volume (in UK/USA units) would cite fluid ounces, and metric would distinguish between grams and cc's...

Glad your formula works well in the other engine! Most diesels prefer well OVER 30% ether in the mix, by volume. Ether is much lighter than water at the same volume. A cubic inch of ether weighs less than 4/5 as much as a cubic inch of water (specific gravity is about 0.7, about 70% of water's.) This works for us, BTW. The 80% cited for the JD would fill about 1.4 rimes as much volume! If the can lists 8 ounces , not fluid ounces, then 80% of the weight - 6.4 ounces - would be over 9 fl oz volume . I presume the 'propellant', the other 20% of the weight, simply gasses off uncaptured.

Suggestion already posted should handle your needs, and I felt a little more understanding of the fuel percentages would also help.

Luck, and success!