Dirt Rider Magazine

i blew my engine on my 2000 xr 100. so i bought a used 1 from ebay which turned out to be a 1985 the problem after switching the motors is i have no spark the new engine only have 1 wire black comming out of the side/top case of motor but my old 1 has 2 which is leaving 1 wire un connected i have no idea of what im doing any help would be greatly appreciated and im thanking the black wire is a ground