The thing is, the Jabiru top end overhaul, is still 1000 hours, isn't it ? which leads to a cost per hour of about 1.5x the rotax, assuming nothing in the rotax breaks.....
The Jab engines still face a sizable problem on AVGAS.
-- AVGAS running ----They don't run hot enough to evap/ gas the lead compounds, so this cakes-up the crown, rings, chamber, guides. and leads to a TEO/TBO of around 400 hours best. This is well known. There is no getting away from this, apart from using Decalin runup with seems to reduce/ eliminate this problem, but not recognized by Jabiru (but is by rotax).
- solution - run ULP95/98. problem solved. Don't run ULP more than a couple of months exposed to air.
Lesser evils
I'm not sure they've completely got on top of the rather inelegant oil pressure control. There's many documented problems. It's OK, just...... and I would have liked to see a heavier thru bolt, since the margin between [ sufficient preload AND the material yield AND tension errors due to torque application on unknown lube threads }
They've gone to much high temperature rated valves, which is good. and about 3x the price per valve, as expected.
and I they've gone to a more solid, non split skirt/crown piston. Gen4s broke alot of pistons before they got that part of it stable.....
Head recession should be a thing of the past. the bolted head , like everyone else, should solve that. In the past, head recession (due to less than ideal choice of aluminium) led to valves hanging open and loss of valves....
Nothing economical is perfect.
-glen