I recently purchased a 1977 dt100 to restore, 
I have noticed to rear wheel is offset to the rear of the frame hoop. The rear wheel is adjusted correctly and sits centred in the swing arm.
Could my dt100 rear frame be bent?
Or are most dt100/mx100/rt100 rear wheels off center to the frame like this from factory?
(Previous owner fitted that tyre, which will be replaced with correct one).
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A pic is worth 1000 words...

 

I tried posting a pic but keep having issues with an error coming up and the file is in the correct format and file size is under the limit.
This is the error - any ideas?
Could Not Move File Into /Homepages/37/D93795775/Htdocs/Yamaha/Media/Kunena/Attachments/16968/0470bc3b30ec868cdfde0ecafc08ef21.

 

Run something long & straight allong the rear wheel & see how it looks at the front wheel with front wheel straight.
Different width tires but gap should be equal both sides of the front with steering straight.
Realy it all starts from sprocket alignment. But there's also vertical incase the arm is twisted.
Do the shocks individualy slide off & on without significant tweeking or compressing other side to get the bolts in.
Hopefully it's just been dropped hard & bent the top subframe over so would need to block it & whack it which is easier said than done.
My 360 is like that & annoys me when i look at it lol so should 'get to it'.
In the old days i would just lay the bike on its side with wood blocks in apropriate places like swingarm pivot point to lay it on, then a good fitting block tapped into the subframe at shock mounts, then another block on the outside at the rear loop. Then a BIG sledge hammer. Plus someone to stand on the front wheel maybe.
Ok i should practice what i preach but not today. First be sure the rear wheel is vertical as could be an easy swinging arm tweek to fix it.
In crash repairs at work i'd have a long heavy steel rod with cones to center it in the steering head, then steel rods verticaly up either side of the rear wheel then decide where to go, but when sprockets are in line everything else sort of revolves around that.
Sorry--too much time on my hands. Sorry about the essay haha.

Can'y find a video of anyone doing it my way, but everything is alloy that came up in videos & there was no loop at the rear where the guard bolts in.
One guy with a similar problem said--he just tied the wheel to a tree & used a Come-Along to pull the subframe to the next tree.
But first you must grow two trees close enough.