Stock main jet is 160. I dropped it to a 150, and there was no change.
To test if the exhaust is restricted, would removing the exhaust system to see if will rev determine if that's the problem?

Well, I learned how to upload video to youtube today.
Here is a link to video showing what the bike sounds like:https://youtu.be/ojH46nBhUxc

Hope this works.

Have to change the setting so it's not private then I'm sure we'll have something to say!

Thanks. I obviously don't have experience posting on youtube. I changed the status to public. I hope it works this time!

not so far.

It is set to public. When I click on this link  :
it works for me. Not sure why it's not working for others.

When I click on the link I see an inverted video of someone walking with camera recording for 5 seconds.
 

No sound? That's the important part.

I hear the sound of a two stroke along with a upside down image going by some houses. I still think you have a plugged up pipe. it sounds like my 1973 Suzuki TS50 did when the pipe was plugged up, when my Dad took a torch to it and it smoked like crazy, once the smoking stopped we put it back on the bike, the bike ran so much better it was hard to believe it was the same bike. this is when I was 13 years old, I am over 50 now btw. That old 50 did not have a silencer in it either.

same thing happened when I put on a Bassani pipe on my 1970 RT1M, until it blew out the mouse nest then it suddenly came alive. like your bike it would not  rev above 3500-4000 rpm at full throttle momentarily then it exploded to 6000 or 7000 rpm with the front wheel up high. or course I had it at full throttle during those revs and it was a wonder I did not loop it out.

was your bike at full throttle in the video or a little lower?

Yep still go with a very blocked pipe. Try it minus the tail muffler & look down in the end where muffler fits in. Have seen them build up a ring of carbon that grows until very restricted. Had a 100 twin where the complete header pipe was full bar a small hole through it all. Reminds me of an IT250 & a PE400 that came to me in a similar state & barely run above 1/4 throttle.