Originally Posted by olas altas
All you need to do is set the piston at the correct TDC (your manual should tell you how)... After you set it to TDC install the camshaft so that the lobs are pointing down and install the cam sprocket and chain so that the timing marks on the sprocket line up with the mating surface on the head. The third mark on the sprocket should be up.
No need to take the rotor off. After you are done, turn the motor over by hand a few times after you get everything lined up to make sure there's no interference for when you go to start it.
It's explained very well here in this quote. make sure the top dead center mark on the rotor is at the top, pointing towards the cam above and follow what's in the quote above.
just rebuilt my top end on my 89 ,fresh bore, new piston , rings , cam chain , valve seals and lapped the valves and head ..
there is a thread here on this forum ( it's a sticky) with a link to down load a free factory manual it's a zipped file in pdf format , (you'll need winzip or winrar to open it and the adobe reader to read the pdf version once unzipped , all free to download ) it's for a 90 xt600E so depending what year you have it maybe certin slight differences .. like 89's and below have seperate oil tanks mounted under the seat , behind the side number plate, while 90 and up the oil tank is in the frame , rear disc brakes 90 and up , also electric start 90 and above and some other small things. But for the major work,, its all the same .