Good news fellow Rotaxers I may have fix for motor!
I use piston stopper that I have make and I discover crank is good so I decide to pull motor and have it stripped.
What was discover was badly worn inlet valve, see picture. Angle edge of valve not matches shape of head seat. Valve is sunk in head and stem is too long by about 1mm.
I will report whether motor is again smooth when I fit motor back in plane :)
If you think you have same problem, test by remove rocker covers, close valves (turn crank) and measure from rocker cover mount face to end of valve stem. All inlet lengths must be about same and all exhaust lengths about same also. If one measure too long perhaps it is like mine? Boroscope may see inside to see angle edge of valve.
valve1.jpg (You do not have access to download this file.)
