RC30, here are some links, let us know what you think!
Titanium bolt kits.... www.mettec.com they will custom make bolts, and axles, also.
Super light and strong sprockets and chains.... www.SidewinderSprockets.com
Billet throttle assembly.... www.TERRYCABLE.com
brake stuff..... www.ebcbrakes.com
Idea for rear shock, On one of my sons pit bikes we used a Fox
racing air shock, what was remarkable was the fact that it only weighed 1.1 lbs I dont know if they have larger model available, but I know they can be valved for many different setups, and are highly adjustable:thumbsup: check them out at.... http://www.foxracing.../moto_index.htm
Heres a 650 that weighs 275, but given the same attention you are giving yours it would weigh 250lbs or less... http://www.build-stuff.com/CRF650.htm
I hope you can get down below 290 maybe even 275, good luck, once again great job of documentation!