Motorcycle Repair: Honda dirt bike, honda xr 100, dirt bike

Question
well i found a 1982 honda xr 100 dirtbike and I am in the process of restoring it and i'm rebuilding the whole top half of the motor, so my question is how do set the timeing chain back to it's factory settings, where does the cam sit, and where does the piston sit, so it is all timed together and runs properly.  

Answer
The piston has to sit at the very top (TDC) called top-dead-centre.  There is a mark on the flywheel that lines up with a mark on the case.  Then there are usually dots or lines on the camshaft sprocket that have to line up with marks or edges on the cylinder head.  The details of the markings vary, so it is essential that you have a service manual for the engine you are working on.  The cam can sit in two positions when you have the piston at TDC, but that typically does not matter since the engine is a wasted spark design.  Good luck with the project,  Jan