I just finished a conversion on a stihl 25.4cc wacker motor. All I can say is wow! Started right up in the cold weather. The first tach reading was 8k on a MAS 16x8. Then I noticed the choke was still part way closed. Opened that up, richened the top end a touch and was getting 9k on the nose with the MAS 16x8. The throttle response was amazing, lightening fast with a reliable stable idle of 1200. I love these einges. The only other prop I had lying around at the moment was a 20x10 mas. I threw it on for fun and got 5k with sluggish response. Interesting but not really useful. The only mods done to the engine were to clean up any carbon deposits(used engine) and I removed the bass gasket and sealed the crankcase with RTV to slightly increase compression. If you can find these engines convert them! Mine came from a stihl weedwacker.