Okey, it has now been in the air for four tanks and is still running strong. The exhaust oil is barely coloured.
Very easy handstarts (no spring starter needed) when priming the side of the piston and backing off the compression screw about 1/8 of a turn. It fires each time and it has only started in the wrong direction once.
Might try to add an exhaust throttle also as it flies more like a clipped wing cub at the moment...