Okay,
if it was a run-away as described, it was possibly a cut or shortened wire from the points in the right mag (actually on the left side in the helo).
The rpm signal comes from a set of points in that mag. The signal wire gets occasionally trapped between the rather sharp edge of the condenser (?..) and the mag cover. Vibration takes it to the wire and you get shorts, with a loss of signal, which the governor reads as low-rpm. Sometimes you can't find this one, as you open the mag cover all looks good. You have to really look close. IF you find the pinch a layer of electrical tape will do until you can replace the signal wire.
Watch the wire routing! Don't get it pinched again.
Oil in the mags is another one. Not always from too much grease in the mag, but from shot mag seals to the engine.
Same thing happened to me with an intermitent "hunting" of the mag - pinched wire.
Despite it seems rather fast the governor is actually slow.
You can check this yourself. When ready for take-off raise the collective rather quickly (still smooth, please!!) and you will raise the rpm, as the correlator is acting way faster than the governor.
Same goes the other way. Just barely touch the ground and lower the collective quickly (see above!!) and rpm comes down.
Governors go out rarely...but you never know.
I would chase the signal wire first, then the points....
Let us know how this one ends!
3top,
