The XJ650RJ(or RJC) are the SECA´s series and they are shaft drive and they were only sold in Canada and the US in 1983. They were called standard bikes back then and have a more upright riding position. The XJ650´s were the MAXIM series and they were also shaft drive but they were more of a cruiser style. The XS650´s were chain drive and sound more like what you have. Don´t get hung up on the stampings. Cheers