I have two DT360s, one handles fine and the other feels unstable, the steering wheel wants to flop to either direction at low speed, I cant take my hands off the bars without it weaving all over the place, it dives into turns with a scary flop at high speeds as well.
I restored the bike from the frame up, it has new everything, I checked:
the wheel alignment with laser
checked for bent chassis with digital level on the rear axle and front end, within 1 degree, no twist.
spokes
new swingarm needle bearings
rear shock preload
different tire pressures, 
checked new forks and wheelbearings all tight and new conditions
tried adjusting steering head tighter and looser, no change
fitted a steering damper but it only masks the problem
checked chassis for cracks
tight engine mounts and triple clamps
I'm not sure what to do at this point, I want to sell it because its not fun to ride like this but I dont want to sell a bike with problems like this to someone. Both of my bikes are on the same tires and I cant figure out what is so different about them.
 

Are there arrows for direction on the tires? Are the fork Springs in spec. Are the pinch bolts on the for triple tree tight and The bars and mounts are tight? Are the Rims the same width with the same tire?
Good Luck and I Hope you figure it out.

First thought is lumpy lower steering races--or top & bottom but weight's on the bottom--causing it to want to stay dead straight but if it escapes the center dent it might just try to get as far from it as it can.
Ok that's streching the imagination but stuffed head races can turn the best rider into a novice again.
Secondly--maybe firstly, if new races are fitted with one too many balls--19x1/4 botton & 22x3/16 top--it'll do something like that but not quite that.
Thirdly--who's counting--if someone has fitted leading axle triples that sit back more in line with the stem--then used straight axle forks that'll turn it crazy--unlikely on your i dare say. Plus the forks would hit the tank on full lock.
Fourthly--if something it causing front wheel to sit on a lean hard to one side it'll want to pull over to the angled side--was common on yamt & honda scooters where they'd had a hard stop into the wall etc & axle lugs on those little arms needed bending to get the wheel vertical,
Fifthly--Umm, time for a cuppa tea.
In theory--well i can--go down the road no hands. Not tried it foir a while. If i don't come back you'll know what happened haha.
One more, reminds me of when RD350's were getting accidend front ended & first one we did with new fork stantions failed to pickup that the alloy sliders were bent. Probably the forks were sticking on assembly which made us look closer.
Wasn't very obvious but could revolve the slider on the fork taking a eyeball line on the damper bolt in the end & became obvious to see. So didn't get caught out twice.
Did try straightening one with limited success but wouldn't recommend doing that unless ya super confidant it's still ok to use.

Fork angle? Longer shocks in the rear? Large OD rear tire? Front end spring sagging?

Sure sounds like something in the steering geometry is different between the two bikes. If you look at them side by side, everything looks the same? Triple tree looks the same, length of forks is the same? Springs operate the same? Any spacers or spring boosters in one that the other one doesn't have?

Where did ya find needle bearings for the swing/arm pivot.
Sounds like a good idea.
Just thinking, bent [twisted over] swing/arm with rear wheel tilted over would do something similar but not as noticeable as if it had the same in the front wheel sitting 'non vertical'.
That reads hard to follow.

How did the bike ride before you restored it?

Thanks for the ideas guys!! I went out and measured the fork angle with digital level on the "good" bike and it measured 31 degrees, and on the bad bike it was 29 degrees. I think the rear shocks are longer!! Ill try swapping those or raising the front. I also bought some tapered head set bearings ill try that too.

I never rode the bike before because it was a hunk o junk.

Triples are all tight, wheels are original, Shinko Trials tires on both bikes at 20psi. Might try even lower.
The swingarm needle bearing kit was for an XS650, I hd to add 1 shim and it worked perfect.
The chassis is straight.
The front fork springs dont sag more than 30% with me on it. I weigh 160lbs.

You will need an assistant to do this.
It is a modification of a technique I used to use for assessing if heavy truck chassis were still true after an accident.  Tools required are string, plumb line and chalk.

Place the bike on a smooth, flat concrete floor.  Get your assistant to hold the bike vertical, steering poining exactly ahead and kept absolutely still, or better still render it immobile and vertical.  The steering and forks must not move.

Take the string and run it down the outside of the fork from the centre of the upper yoke to the center of the axle.
This will tell you if the leg is true.  Keeping the same datum points, run the string to the ground still in a straight line all the way from the upper yoke through axle center to the ground.

Mark where it touches with the chalk.

Take your plumb line and from the centre of the axle mark exactly where the plumbob touches the floor.

Measure the distance between the chalk marks, record it and do the same on the other fork leg.  They should be the same probably within 1/8th of an inch.
You have 4 chalk marks on the floor.  Forward ones are rake and rear ones are castor.

Measure the distance between your rake marks, halve it and place a mark.  Do the same with the castor lines.

Draw a dead straight line between the two marks you just made.

Take two pieces of string and connect your left hand rake mark with your right hand castor mark diagonally.

Do the same with your other two marks.

The point where the two strings cross should be bang on the centre line you made.  If not, something is twisted.

Compare your results with your other bike.

I would suggest putting the front end of the bike that handles ok, into the one that doesn't, and see if that helps. Other things to check are rear shocks, and if the wheels have been rebuilt, are the offsets correct.