It was at full throttle. That's all it will do.

thanks for the response. I will check out the tail pipe.

BTW, the weird video was taken while I was riding down the street with one hand on the throttle, holding my phone near the engine with the other hand in order to capture the sound. It just so happened I had the phone upside down. Should have just held  the camera with it pointing towards the engine so it would have been easier to see what was going on!

Audio was more important & that was excellent thanks. I guess it was held wide open or something like it, as sounded constant. More open than the revs where its limit to anyway.
Just thinking, apart from what i've said in other posts, you could space the pipe back at the cylinder with a few washers between flange & cylinder on each stud to let it exhaust freely to a point but not get arrested for noise, Well, not a big lot of noise like if the exhaust was removed totally. First job still is remove tail muffler though as be surprised if its not in there.

Thanks for your response. Yeah, it was taken with the throttle wide open.
I will check out the exhaust system this week, and hopefully resolve the problem.
I want to ride this thing!

Keep us posted!

piston in back to front--no, be all lean to the extreme not rich. ignore that.

I can't remember the everything that was done...  are you sure the o-ring on the bottom of the jet setter is sealing good to the float bowl? 

I think 75 was the last year they used that system...  even though they didn't need it anymore.

I did replace the oring. When I put the bowl back on, it felt like it was sealing. Is there some way to test if it is sealing properly?

A little grease on the O-ring will help seat it where it needs to be to seal well, and it will help tearing the O-ring as well.