ORIGINAL: energyman
Airraptor,
Attached is a picture taken on Wednesday afternoon with the temperatore in the low 80's. Fuel was Omega FAI, APC 11x7, 10mm Carb. Sometime, as in the picture in post #4, the peak varies. Don't know why; phases of the moon, humidity, new haircut, etc. I have two of these engines. 24.4mm stroke, 22.7mm bore measured. The Jett Stream is the
JS-90 version with 42mm spacing requiring no engine adaptor for the Rossi.
Danny
The 14,250 ground rpm shown there is right in the meat of the jett-stream tuning band. For ground rpm, that is perfect. For flight, you would want to set the needle on the rich side of peak rpm down about 600-800 rpm. So figure on 13,500 for launch.
Once in flight, it would unload another 500-800 rpm or so above that ground peak and it will need the extra fuel.
It is not worthwhile worrying about rpm variation of +/- 300 rpm or so - all engines will do that based on temperature/humidity/altitude, etc. Very common. Get a good reference rpm by running the engine on the test stand a few times, and you will have an idea of where it should be. For flight, just find the peak for that given day, back it off as noted, and fly it.
Bob