Vintage Dirt Bike Q & A

friend gave me a basket case cr125 , was missing cylinder and atac system, have head, bought a cylinder from ebay suppose to be a85 , got motor put together and head studs differnt pattern, so buy another from ebay again says 85, get it and sombody has big bore sleeve, it turns out to be a 84, when did the head stud pattern change 86? the 84 jug is not as tall, so i dont think i can use that , but my 85 head matches stud pattern. bought a lot of new parts brake cables , sprockets etc etc so im committed to finish now, restoring for my son. should of just bought a running bike. was told this is the place to ask, after making several calls , nobody seems to beable to answer, thanks ahead tim , also did get atac pipe that was gutted with one of my cylinders, should i try to get complete system or use this, they have everything blocked off.