I need to know what size jet to use I like riding woods and the dunes I have a cool head with a 21 or 22 cc dome radvalve fmf fatty torque pipe and silencer bored .050 over port job and a uni filter it is a stock carb and is it hard to change these or not

 

It's very easy to change main jets on a stock carb. Take a 17mm box wrench, feel the bottom of the carb, that hex is 17mm. Shut off the gas, take that plug out. Straight in from there is the main jet. Use a 6mm socket and take it out. To replace, do the opposite.
It's really hard to tell what jet to use. Start by doing a plug check. Warm you engine up, take it for a ride, get it good and warm, then pin the throttle for several seconds in 3rd or 4th gear. While you have it pinned, pull in the clutch and shut off the engine and coast to a stop. Pull the plug out. Any white at all, you are too lean and need to go larger on the main jet. Black and oily, too fat and you need to go down size. If it looks like the color of a paper bag, light tan, it's just right.