Running fine at WOT then dies!

Check you fuel tank cap for proper venting. Sounds like a fuel flow problem. Try leaving the cap on the tank loose and see what happens. Let us know, please.
Tom

bairdco said:

how much of an angle is your engine on?

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I think what Baird was asking was carburetor angle, not so much engine angle. The carb should set reasonably level for the float to function properly.
Have you confirmed a good flow of fuel? Disconnect the fuel line from the carburetor and open the petcock. Anything more than a drip will suffice. If it only drips then you have a restriction in either the petcock or the in-tank filter which is attached, or should be, to the petcock inlet.
Carburetor float level is another possibility to check. Too low and you could be starving for fuel at high engine loads. By too low I mean the float is shutting off the fuel prematurely and leaving the bowl with less fuel that the engine requires. A high float level will promote flooding and fuel leaks at the carb.
If all looks good with the fuel/carb/float then start looking at your ignition. Do you have good connections at the spark plug wire at the CDI and top of the plug? What spark plug gap are you running? Check these things and get back to us, please.
Tom