tire pressure for 125cc

my 125 pit bike has 10" or 12" rear and 12"or 14" front

i weigh like 100 pounds and where i am going to ride is very sandy and rocky

any suggestions?

i would go with 25 to 30 psi.......

Look at the tire manufacturers suggested air pressure on the sidewall of the tire. If you are going to be riding fast and there are lots of rocks, use the pressure on the high side of recommended to prevent pinch flats. Generally when riding sand use lower air pressure to give the tire a wider footprint and better flotation, but air up for rocks unless speeds are lower and your crawling up paths.