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[Presto]

The figures are approx 100:1 at idle and about 30:1 at full load.

[hubb]

I have run a 56 year old villiers for many years and after one of its many re-builds I tried running it on a modern two-stroke oil. It may have been my imagination but it seemed not to like it and ran much more happily when I reverted to an old 20/50 oil mixed at 24ish to 1.On no account use Castrol R,not even a spoonful to get the smell. PeteF makes a good point about the exhaust and the timing has to be absolutely spot-on for optimum performance. ATB, john

[Scalyback]

[center]


Smaty pants here posted the wrong bike didn't I??? It's a 150, sorry!

[Hopeless Rider]

Several things that you can look at. First these engines are regarded as low compression at 6 ½ to 1 so using 97 gas will have no advantage and will be effected by the original ignition timing which will be set up more for 88 to 91 oct. Issues over the correct fuel/oil ratio can be confusing but generally a good mineral 2 stroke oil is suitable for ratios up to 35:1. When ratios of 50:1 are quoted this is more for synthetic 2 stroke oils and are not recommended for the older 2 stroke motors. Besides different piston type materials causing piston seizures synthetic oils can cause premature wearing of the older big end bearings. Used really for late model machines as recommended by the manufacturer or for those who are after the ultimate in performance who believe that less oil is more power. This however can also be misleading. I used to race a air cooled Honda (am I allowed to use this word on this site???) CR480 with a good mineral oil at 25:1. However the recommendation from Honda for maximum performance (hp) was tested at a mix of 20:1.
The issue with the air filter is interesting and may be more centered around the piston and rings. With only 4300 miles on the bike has the piston and rings been checked? If the rings are partially sticking through sitting or if there is excessive piston clearance 2 stroke engines can start and rev freely whilst not on load, however when loaded up ie riding, you can end up with excessive piston blow-by causing the crankcase to only partially fill with fresh fuel from the carb. By taking off the air filter (really a gauze to stop the big chunky bits going inside) you are providing less restriction for the gas intake on the induction stroke which is balanced out against the poor crankcase vaccumm from the problem with the rings. Just a thort Batman.
And Enfield claimed in 1953 that the top speed of the Ensign was 50~55mph. Do we believe them or just a marketing ploy to rid the world of those pesky Bantams!!