Thats right there isnt a set temp spec. But I do have a IR temp gun and I use it to make compairisons to changes . I always take the temps in the same place. Glowplug base and from about 3 inches away . I know the numbers I see are of no use but to myself . Just like JVB started this post looking for info. I sure would hate to think that the only info he got was from guys saying checking temps is B*ll S**t . Air cooled engine for the most part will always very in temps and are very much effected from ambiant air temp. I personaly Love info and I check compression of all my engines from new to used and temps and so on and I have the ifo recorded in my shopbook . I know this info serves only me but then I also use after run oil LOL.