Exhaust studs

I learned something new about exhaust studs recently when a customer questioned why he could not thread a nut on one end of a stud.

Although the thread on both ends of a Z1/KZ900 exhaust studs is 6mm and both ends are the same thread pitch, the threads are NOT the same. The end that threads into the engine has a slightly larger diameter (2-3 thousandths of an inch) thread to ensure they hold tighter in the aluminum head. I checked some other diameter studs and found the same thing.

It makes sense given the different expansion rates of metal.

correct! but loctite helps;)