ok i have everything needed to chang a piston but i just dont know how to get the old piston off the rod to get the new one on
plz help

 

You need a repair manual.

 

just pull the wrist pin clips out and be careful that they dont fall in to the bottom end then slide out the wrist pin and remove the piston.

 

How do you get the wrist pins out ?

 

There are circlips on each end of the wrist pin. There is a little groove on the piston that will allow you to use a pick or small pointy tool to release the clips. Like mentioned...put your hand over the clips...and put a rag over the exposed engine...do not drop the clip. The wrost pin will just slide out after that.

pay attention to which direction you put the piston back in...there is usually an arrow pointing towards the front of the engine. This is important or the exaust/intake ports will not be lined up.

also make sure the rings are staggered on the line up pegs. check your ring gap...and torque everything back to spec.

that is the basic explaination...you really should consider a manual.
You will find it to be a simple simple job...but it has to be put back together in the right fashion.