I need to figure out both the size of the part that goes into the headtube, so that I buy the correct replacement. Do I measure the diameter or just lay it on a ruler and measure the width of the tube?
And I need to know how to figure out how to measure the rise of the part that clamps onto the handle bars.
I need to get a longer stem that what I have, by about an inch or so.
You have a 1" quill. Measure from the head of the expansion bolt to the center of the clamp circle, then add the 20-30mm you want. If you're keeping the same handlebars, you'll need to measure the diameter of the bars at the clamp. Will probably be either 25.4mm or 26.0mm, unless your bike was equipped with Cinelli bars and stem, in which case you'll have a 26.4mm clamp and will need to buy a Cinelli stem.
edit: if yours is a factory stock 720, you have a Cinelli 1A 26.4 clamp stem. I have a Cinelli 130mm XA 26.4mm stem in my eBay stuff for sale (signature link)
Thank you, I do have have the factory stock Cinelli stem and handlebars, but the stem is too short and I do not really like the handlebars. So I may have to change the handlebars and the stem to get the reach and level I want. I want the handlebars just below or at the same level and the saddle.
the current height of my bars are good, I just feel a bit cramped. When I measure the seatpost to handlebar length on both my bikes there is just over an inch difference between them but standing side by side the handle bars and saddles are at or nearly at the exact same height.
I am thinking about about the stem you have, vpiuva, because that would make the both bike fit almost the same. And my other bike fit very comfortably.