stupid kick back you wait till you start it kicks back and u hit your front break resivoir with a extra long bolt coming through it OUCH it really hurts..
well hey you suplied me with the scietific stuff there mate it kinda makes sence to me lol :D haha so what you say is if you use high octain in low compresion engine all the fuel doesnt get burt?? and if you use low octain in high comp engine it will burn it all up and want moore??? makes sence...
take piston of get sand blasting gun fill it up with bi-carbonated soda and blast the carbon of the head and piston.
then lean it out a bit. or if its oil residue maybe you rings are worn heaps how long ago did you change them?