My Trail Tech (DT400B)
 

I need a couple or three of those...

That is a neat little gauge but they are expensive.
I'll probably stick to carrying my little hand held temp gauge for a while and do some regular temp checks, if I dont see it rising too high then I dont think I need to worry, mind you I still might by myself a Trail Tech gauge eventually.

Thanks Andy_C, I’ve moved the clip to the 3rd position (lowered the needle) and the ride has vastly improved. The only thing not stock on my bike is the Rex Speedshop ignition (same as yours). I wonder if the reason for having to change the clip position has anything to do with the Rex Speedshop ignition?
I think I just need to have a play around with the air screw and I’m done.

Perhaps the Rex's conversion gives a better spark than the stock setup, or the timing is slightly diffrent than stock.
Worthwhile having a fiddle with the air screw, it does affect acceleration and the degree of surging on the overrun - seems to be a compromise, as I am sure you will find out.
Good to hear that moving the clip has improved your ride - I will try and post up a picture of the plug so you can see the colour, I think it is pretty good myself, but would appreciate any other thoughts.
 

Per JammyWammy's comment... mine does not rev smoothly through the entire rev range... I find I'm shifting early to avoid sputtering/farting.. wonder if this could be any number of things or, ideally, something readily identifiable and specific.

Going by my experience with my DT after getting it ported and a larger carb I'd say it's running too rich and your main jet is too big.