Which way does the slant head go?

Ok here is a pic of the top of the piston my misses took it so it doesnt really show what I was hoping to show but you can clearly see the whole top of the piston is black.

The plug look a little on the rich side coz I let it idle for a min or 2 before I shut it off but all the prongs are the same in colour I didnt wanna go to the point of taking a side pic of each prong but you get the idea.

You will see abit of blackon the piston I know this sounds lame but I do tend to run the motor a tad on the rich side in mix and and rich side in fuel. I have a theory that it'll keep the motor cooler in our hot summer days we tend to get here in OZ atm (for the long rides to work I have to do) it may rob abit of performance but thats something else.

FYI.. observation from an experiment.
I went for a 5min speed ride up the hill full throttle then back down the hill full throttle with lightly applying the brakes to really get it hot in a short space of time.
Jumped straight of and took these pics one after another as quick as possible.
The pic showing the temp at the front of the head shows a max. temp of 180celcius beneath the actual temp of the head that 180 was a the zorst temp.

The fotos were taken in the order of front, back, carby in the space of about 20sec.