How hot?

What kind of temperature should you be expecting out of a KX125 from the engine?

I've just leaned out my karb on my kx from the factory settings which were WAY too rich.
started it up and it sounds great and for the first time since i've had it, it actually really goes. The kick that it now has in the bottom end is unreal but anway.
i noticed that after revving it for about 2-4 mins whilst i was in neutral the chamber really started to get hot.
now, i know they get hot (i'm not that dumb!) but it just seemed to get hot very quickly.
i could be just going over the top here but i really don't want a seized engine already.
i can't believe that it is too lean cause even though it is better than it was before, it is still getting the plug a little oily but only very very slightly (the majority of the ceramic part is turning the sandy colour) and i only made tiny adjustments. i leaned it down 1 step on all jets.
So am I being paraniod, is the bike actually doing what it should be doing now? or am i gonna have to start saving for a new engine already??


p.s. the weather here has been warm, not hot, just dry and warm.

also, is there a quick and easy way to know if you have jetted it right and if it is too lean.
obviously it's pretty easy to tell when it's too rich.