The aero guys are using cdi systems and spark plugs to convert 4 stroke nitro to petrol/gas.
They still require oil mixed with the fuel to look after the engine though.
have a read of this
http://www.justengines.co.uk/acatalo...xperience.html
the key if running 4 stroke is that the torque of the motor is much higher at lower rpm, setting a clutch is going to be really tricky. You would need a very soft spring to get the earlier engagement and i would guess gearing would need to be differant. If i had the cash i would love to try and work with one of the existing 4 strokes and see how viable this is