Hello and Merry Christmas I have a problem with a torn-down stand-up bolt on the cylinder head and would like to, since it is flushly torn off to weld a nut, with drilling it will be difficult at this point it is the extreme stand-up bolt in driving direction. My question would be, is it just enough to disconnect the battery or should I still separate the control unit from the engine and the gas system? Or completely different procedure? Motor is the B5252S Greeting Michael