Anyone know what make frame this is?

[GTO]

Weird.

 

[drheilman]

More pics of the rear axle, and motor mount area, please.

 

[GTO]

This is the only other pic.

 

[steven Durham]

Well I hope the seat finds a better mounting LOL Any number of frame manufactures could have been the maker. It is from the 80's because of the style of the front end design and I see an Airheart master cylinder.
If it's yours it should make your son very happy. Now all you need is a new Briggs Blockzilla motor and a nice Horstman X5-D Clutch
OH yes a good helmet Steve

 

[shoe]

I think its a Margay