Good thoughts there, Geoff. I do use a quality oil, changed at least as twice as often as recommended, & have done since I've owned it, 10 years & 28k.
I don't think the engine is high revving - it's basically an oversized Cub.
It started smoking & using oil. Did a compression test, it was under half what it should have been. The head/valves were quite carbonised, apparently.
Bru.