First, I do not think your ped is a model 7 unless they made 2 different kinds. My model 7's have no rear suspension and a big 7 on each side of the frame below the tank. I think you have a Model 40 or 50.
Second, most ped swingarms (rear forks) are mounted in flexible rubber bushings which have the center metal tube bolted rigidly to the frame and the outer metal tube pressed into the fork. These bushings are bonded into one piece and motion is provided by flexing the rubber. After removing the wheel and shocks, look carefully at the bushings and the bolt as you move the swingarm up and down. Determine where the bolt is frozen and proceed accordingly. If a bushing is frozen to the bolt, don't try the long wrench trick, you will break the rubber bond and destroy the bushing. Do not use heat as this will destroy the rubber bond also.
If it is the bushing, your only hope is a good penetrating fluid (WD40 is not) and appy it for several days then try to drive the bolt straight out, maybe with the nut protecting the end of the bolt and using a brass hammer or a piece of hardwood. Have someone hold a big piece of wood on the other side to provide some support. If the bolt is frozen to a solid metal part (not the inside of a rubber bushing) you can use a big wrench to work it back and forth til it breaks free. Use lots of penetrating fluid and try to just load the bolt one way then the other without twisting it. The idea is to flex the bolt, not permanently twist it, as this will most likely break the bolt.
By the way, your air box and carb look like mine so I should be able to help with tuning.