Thruster,
The Jabiru engine will typically get stiff when the barrels distort when hot. You can check this by carrying out the following procedure:
1. hand swing your prop to checking all the compressions and more importantly checking for stiffness when the engine is cold.
2. Run the engine for 2 mins at 1200 rpm and then shut down
3. Hand swing the engine again and check for stiffness.
if the engine feels stiffer then it is because the barrels are beginning to distort. I say this because after 2 min at 1200 rpm only the barrels get hot.
Rule of thumb. If you fly the aircraft and shut down always watch the prop. If it kicks back then the engine is acceptable.
If the engine gets really stiff then it will need remedial work. Essentially this means removing and honing the barrels and using re-worked barrel base nuts. When re-torquing, check for barrel going stiff using a hot air gun.
Roger Lewis