I built a 4*120 and originally intended to use a Ryobi 31cc engine. I moved the firewall back about 1.25". I changed my mind on the engine because I have to use the family van to transport the planes to the flying field and didn't want the smell of gas. I instead mounted a Super Tigre G 2300 and using a 16X7 APC prop and a Bisson Pitts muffler. I plugged one of the pipes and ran about a half gallon through it on the test stand. At this point I have about a dozen flights and it appears to be a good combination. Run the engine at mostly half throttle with plenty of power. I agree with Taildrager that the 91FX might not be big enough for the plane. I have no experience with the 91FX so it's just an educated guess on my part. Try a search on the 4*120 here at RCU and you should find some posts mentioning the engine also.





quote]ORIGINAL: Phuzzy

Hey All

I am just about to start a SIG Four Star 120 building project. And have an engine question, I have looked at just about every thread as far as 4*120's go and cant quite find an opinion on my question. I am flying a trainer at the moment (SIG LT-40) and the 4* is my second plane. I am not too sure what engine to put in. I am leaning towards a Saito 120 but also concidering an OS FX 91. for simplicity's sake, I have no experience with 4 strokes. Because wher I live Johannesburg, South Africa we are about 5000 ft above sea level and my LHS said the FX91 will be underpowered and suggested an Irvine 150. Any comments?

Marcel
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