Originally Posted by Czech-it-Out Graphics

black is carbon build up, that is due to running rich and you will see that on the top of the piston only. You dont need after run oil, it really is pointless and will only foul plugs if u run a good fuel. Run the motor out of fuel and you are left with an oily mess, there is your after run oil. you just dont want to leave un burnt fuel in the motor that is what creates the rust