How square and true is the stock frame, KZ750

building a hardtail kz750 (82) with a tc bros universal kit and im measuring myself to death and wondering, how square was the stock frame to begin with?? i am doing a single backbone, which is a piece of 1-3/4 .120 wall which fits perfectly over the stock backbone. mines a little longer of-course. when cutting the triple backbone section out i noticed one of the two "side-backbones" was closer to the center one than the other, so that right there is something out of square, i guess... cut to me wearing out all measuring devices in my garage fighting for an 1/8" here or 1/16" there, but how can i be certain that any point on the stock frame is truly "where it should be"?? is there an acceptable amount of off-ness allowed lol?

German magazine MOTORRAD tested several frames from the big 4 plus BMW back in 1981 and those from BMW and Kawasaki were perfect, the others save Honda acceptable and the Honda pipes so madly out of spec in every direction that the tester at first refused to believe they weren't crash damaged.

it was common for the kz necks to be off center. as long as u have a few main point right u will be fine. i think the most improtant thing would be ,the front axle should be true to the swingarm pivot. the front and rear rims centers can be off a 1/4" with no problem. unless of course,u are going to race in a serious class.

thank you, that makes me feel much better! and no, no racing happening here. i am surprised at how ugly MOST of the welds are on the frame, some even barely catch the part they are holding on.

maybe try putting a rod through the front axle and swingarm pivot. find a way to make them sit true to the bores. then u could measure the distance between both ends, front to back. i think this would give u an idea if they were true to each other. u also want to see if they are parallel to each other.
the rear axle should be fine as long as the swingarm is straight. but u can realign the back wheel to be true to the front easily. it doesn’t matter if they are not inline, but should be perpendicular.

my problem was the backbone. i did a single backbone and simply sleeved the stock one. turns out, the stock backbone doesnt point straight back to the centerline of the rear axle, its a little off to the left. i fought and fought this trying to build around it and once in a roller the wheels are fine but i know ive built in a 1/4 of an inch of off-ness into the hardtail just account for the backbones' error. so now it bugs me to death, but everything will work just fine. i am tempted to cut it all out and replace the stock backbone entirely, but i have to keep telling myself, "you got the bike for 300 bucks!" im sure noone but me will ever look at the bike and say, this side looks a tad different...lol