where to start?

I made a deal and have recieved a 1981 kz100j and what I believe was a 1982 gpz 750 both are in a large pile of parts. The 750 motor has a damaged block, a chunck on the right where the points would be is missing.

So where should one start in putting such a pile back together?

Start preping the frame and wire it up...Then ready ye motor for the install.

id see if the motor or motors will turn over first and run a leak down test before putting it in the frame since its already out

Indeed. Ready thy engine before installing......

Figure what you want to do.......are there 2 bikes? Do you want them both? Personally, I would start putting them together, at least motor, wiring, etc. to see if they will run.

Now post some pics!

the motor does turn over. what do I need to do a leakdown test?

i'm thinking you shouldn't mess around you just should box up every thing and send it to some of our more deserving members i won't mention any names(ME) actually seriously i'd do a compression test every body has a compression tester a leackdown tester is a bit more advanced for right now does either engine still have the starter motor still on it. if so get a booster battery and some cables hook the positive lead from the positive side of the battery to the output stud on the starter then hook the ground up the negative side of the battery then touch the engine anywhere and if you have a good battery and there is nothing wrong with you cables then the motor will spin over like a bastard. remember to pull all your sparkplugs first to make it easier to spin install the compression gauge. crank it over until the gauge stop's moving and take your reading then move to the next hole. remember to hook the battery up the way i say as gases are being produced that explosive and if you arc by the battery it could explode which speaking frm experiance is not fun. good luck hope this help's

For information on leak down testing and how to make a relatively inexpensive gauge, go to the menu bar above. Hold the mouse pointer over "KZ Information." Click on "Filebase." Look for a file called "Leak Down Test."