Compression test on a 2 t KTM????

Hello people I want to get a 2-stroke KTm, with road registration, to the fieldway cracking. How durable are such engines????? how do I check the compression??????? on the 2Tacter because you can not hear much about the wear, right???? what costs about a new piston with cylinder loops, or crank drive over?????? are the parts with the Japanese cheaper????? am grateful for every tip roland