Thanks for the response, guys, & the support! I have already begun experimenting with different sprockets, and that has made a huge difference. As an side note, I noticed lots of comments about top speed & sprocket ratios. You may be interested in my calulations. With stock 14T/47T sprockets, the beast should be capable of slightly over 100mph (at 10,000 rpm engine speed).
I am currently experimenting with 13T/52T! That's lower than anyone recommended, but puts the bike very near the same overall gearing as the KX250. Of course it pulls like a tractor, but that's OK. If I keep it geared this way, I will definitly try some flywheel weight, as every ding, ding, ding of the engine is transmitted as a umph, umph, umph to the bike, when going slow!
Slowing the bike down will be easy enough. But making it happy is my challenge now. I have raised the needle clip one notch (to position 2) and dropped down one size on the pilot jet. Still running stock #8 plug. Bike is smoky and sputtery until it get's hot & then it clears up. I'm still running 32:1 mix. Thinking about trying 40:1. Any thoughts?