Mine tends to want to be a bit higher when the oil is “cold”. That is, the initial takeoff of the day. But it doesn’t vary wildly. Since yours has shown itself considerably low for over a decade it wouldn’t seem to be governor wear. I can think of two things:Tim H wrote: ↑Fri Oct 22, 2021 12:03 am
One thing I noticed is the RPM seems to be higher in colder temps. Does the temp impact max RPM and if so if the prop is adjusted in cold weather then it won't make max RPM in warm weather and if its adjusted in warm weather then it might overspeed in cold weather?
Is it time for a governor overhaul since the adjustment is at the max RPM and I'm not making max RPM?
1. There is an adjustment screw in the hub that restricts how “flat” the blades can possibly go. This should be properly set at manufacture and/or overhaul. A way to see if this is the limit is put the plane in a bit of a dive with the prop lever full forward. If the RPM increases substantially this is probably a factor.
2. This is a little trickier to explain, but the travel of the lever that rotates the control shaft of the governor may need “reclocking”. It’s a spline joint. By repositioning the lever on this spline one can bias the entire setting range to higher RPM. So the max limit is now higher.