Problems at high speeds.

[His Dudeness]

You've confirmed spark and that your plug caps are on the correct cylinder right? So we're calling spark good. Compression was good before so it's probably good. Air filter I think you checked so air is good. Fuel seems the only question mark but no matter what you do to the carbs choke on/off, idle mixture screws adjusted, idle speed in or out, it all seems to make ZERO difference to the bike trying to start so to me that points to there not being enough fuel going into the carbs or not enough fuel getting through the carbs. After the work you've done it seems unlikely the carbs are blocked so I think the fuel supply into the carbs could be the issue. Try hooking up another fuel supply like a funnel or a bottle straight to the pipe that feeds the carbs and try and start it. Or try the easy start into the air box. If you're sick of working on it get a mechanic to look at it. It seems to be a frustrating problem but I don't think it's a massive one so you'll only regret selling the bike