I just bought a ´75 dt175b (?). I don´t know much about these bikes. It´s been 30 years since i´ve even seen one of these. Any help would be appreciated. I bought for me to play with ( fix up, paint, etc. ) and my son 14 years old to play on. it runs good considering. the petcock leaks and I´m not sure what kink of oil to use ( those seventies are kind of a blur). Thank You. G.W.