hi i have just bought a plane with an os gemini 240 4 stroke which has been converted to petrol the person i bought it off has not done the conversion and says it was done by someone else but does says that he was told that 35/1 mix is fine as far as i can tell the engine has not had any other mods apart from the ch ignition
has any one else done this conversion and know what mix i should use glow fuel should have 16% oil but this would be in the region of 7.5/1 and would foul the plugs
any help please

Most gassers are fine at 35:1 or 40:1. Often chainsaws ad such simply say: "Follow directions on oil container."

I don't think your nice and expensive OS Gemini will live for very long at 35:1 oil mix. The glow 4stroke conversion has many reasons why you cannot go lower on the oil mix, especially with gasoline. 1st, unlike 2stroke conversions, which has the fuel-oil mixture go through the crankcase before going into the combustion chamber, 4stroke glow engines rely entirely on blowbys for lower end lubrication. The higher stochiometric (ideal) mixture means that for every conbustion cycle, there is much less overall oil contained within the fuel-oil mix. Less oil going into the combustion chamber meand even less getting blown by the piston rings into the lower end as combustion remenants.

Even though gasoline has some inherent lubricity, whereas methanol does not, it helps the 4stroke very little because the raw fuel does not go through the lower end first. Most of the gasoline that gets inducted into the combustion chamber ends up getting burnt off and very little of it, if any, gets blown by into the lower end.

If the conversion was done right, it would have some sort of oiling system added to the engine. If not, you best bet is to mix in plenty of oil with your gasoline.