OK I got one of these today and never trying a 4 stroke would someone tell me something about it. I did not get the box or any information about it but there are no mounting marks on the tabs - Looks like a new engine that was stored.

Is it an engine we can use for stunt or does it need modifying?

I understand that the 4-stroke engine puts out more power. How is that power transmitted to the aircraft? Is the power of the 4-stroke utilized by increased rpm or by use of a larger diameter prop? Reasoning would say that use of a more powerful engine to turn the same prop at the same rpm would offer no advantage - the prop would displace the same amount of air if it turned at the same rpm.  If the engine turned at a higher rpm then the result would be higher speeds - this would not allow the plane to fly slow - a lower pitch prop would be needed to slow the plane so the result would be wasted power. It would seem the only way to utilize the power would be to increase the diameter of the propeller - and this might be something that is not wanted because of ground clearance. My questions are: Does the 4-stroke turn higher speeds or do you use a larger prop?
 
There is a lot more metal in the 4-stroke - pushrods, valves etc and there is a carb hung on it. On a normal 2-stroke engine it is relatively simple to remove the carb and insert a venturi with Needle assembly. Wouldn't it be to my advantage to remove this carb assembly and replace it with a venturi? Who would I contact to fabricate this  and would there be a weight savings by doing so?

I used one of these on a stuntwagon. It pulled this plane along with a lot of power. 12x5 or 6 prop 10% rojett fuel. The choke is nice to get it primed, hand starting was easy. George