Cannot get over 4800 RPM STATIC
I just purchased a Remos G-600. On my initial test flight I believe we were getting 55 to 5600 RPMs. The plane and sat for approximately a year. On subsequent flights the RPM continually continues to drop. Now at static I can only get about 4700 RPMs. The plane just had the carbs synchronized before I bought it, and a current annual. We did fly a couple of times with half of a tank old fuel plus new fuel. Since then I have flown approximately three tanks of fuel. At level flight I cannot get over 5000 RPM. I am change the fuel filter, check the air filter, and put new plugs in. Short of rebuilding the carburetors does anyone have any ideas?