The rear tire tracks square with (in line with) the front tire. If your rear wheel is offset you will see it when looking from the rear. Move your eye (just one! ;) ) from side to side thru the centerline of the rear wheel when the front is straight. You should see the occlusion of the front tire (because the rear tire is in the way, 'eh?) evenly from side to side.
I looked at my bike last night with spoke spacing in mind. They are not all the same, certainly. Generally, the rotor side is further apart than the sprocket side. I'm talking about differences in the 1/16" or so range.
I DID find a loose one, too! OF course, tightening it back up was a lesson in futility.
This has been in the 'new bike prep' type threads before. ANTISEIZE your spokes/nipples when the bike is new, or you won't likely be doing it later. Solvents and heatnotwithstanding.
Listen to canyncarvr!!! I did almost all of the standard new bike prep when I took my 200 off of the showroom floor; greasing every bearing that could be seen w/out spliting the cases, oil changes, tire pressure, airbox sealing, new plug, fresh gas, and every other tip published in Dirt Rider within the last 13-15 years. I checked the spokes after every ride, as the manual suggests. The first time that I found any loose (4 of them) after a weedend trip, three were clipped and replaced w/ new nipples, and the fourth ate a half can of PB blaster before succoming to my demands. I wouldn't advise the use of heat unless this tecnique has been mastered in the past, I've witnessed several others introduce themselves into the market for new rims (an individual looking to replace an EXCELL seemed particularly perturbed). Duct tape the inside drop-center of your rims and use anti-sieze on the spoke threads.
After tightening a few loose spokes, the back wheel lost its wobble and seemed to regain its "circleness". Yes the rotor side is a bit different in spoke spacing w/in 1/16 for most and maintains tracking w/ front tire. Kind of disappointed, I was thinking maybe I "had" to get the black Excell rims. Maybe the ground will thaw out soon - going insane!!