Re: How to tune an engine with a temp gauge?
I fully agree about the angle fire heads, they just can't get rid of the heat fast enough, then add a few performance upgrades and the problem only gets worse. The Puch heads do the job very well and cost half the price of a Fred head, not saying anything bad about Fred's heads because I run one on mine and it keeps the engine way cool. The fred head is more compact so it fits better in tight frames, but other than that, either head will keep your engine plenty cool enough.
I'm not completely up on my C to F conversion either but 150C should be around 330F or so, which is still in the safe zone but getting close to your limit. I like to keep mine under 360F which is about the max allowable temp for short bursts, not good to run it that hot constantly so try to tune well under that temp.
Be careful with the tuning here because like Theon said, it will make more power when you go leaner but it's also running hotter and won't last as long, many people have blown their engines going with the "lean is mean" tuning, there are other ways to make big power without burning up your engine and we can go over that later on if you want to know.