Engine not making full power

Get an optical tach so that you will know actual RPM. A leaking primer can cause an overly rich condition. Getting an extra 175 RPM when leaning does indicate a fuel problem. I have never had more than 50 increase when leaning at 1700. Static RPM should be 1900-2100. Primer rebuild kits are cheap and easy to install. Your mechanic can even plug your primer line for test purposes. What is your rate of climb? I do not recommend full lean at full power. That is how valves burn.

Bill,
Did you ever get any resolution to this? My coupe 99705 acts very similar. One question I had for you is where does your coupe cruise at with these issues? The best I can get at 2250 is 85 winows open and 95 windows closed. My engine also runs hot but, I feel that could be because it is flying to slow?

Engine is C85-12f, TSMOH 1088, TSTOH 151 hours. Mags are Eisemann, carb is Stromberg, carb overhaul 4 years ago, prop is MacCauley 71-50 with fresh overhaul. Mag checks are good at 1700 rpm. Left mag 70 rpm drop, right mag 45 rpm drop. Engine acts like its running rough and rich. (Airport elevation 665, Density altitude 2100) Ground run static rpm is ~2000, but if I lean carb I can get 2175rpm. Full lean at full throttle engine runs rough, but will not quit running. In level flight at 2000 MSL, full throttle, I get about 2350 RPM when I used to get 2525. Leaning helps some, but is not steady or consistent. Plane is typically flown 90-100 hours/year last 10 years and this is a first. Can a leaking primer cause this? What else should I consider?


Bill Chalker
N94191