With regard to the sort of things to look for with Jab engines, having a look at the Jab engine manual there are bushes in the rocker arms whic at a guess would be some kind of bronze( copper tin etc.) Valve guides are likely to be similar. The main bearings are slipper bearings so most probably white metal (antimony ,tin ,lead zinc). then of course valve lifters and cam shaft these as I'm sure you are aware are the bits likely to wear. Jabaru should be able to tell you the chemical compositions of these components and this should give you a pretty good guide as to what to look for in your oil analysis.