2008 KTM 300 reving problem?? please help? STORIE UPDATE

[PHILIPKUHN]

I bought a 300, new aircleaner; correctly oiled, new sparkplug, carb is clean; air screw 1 1/2 turns out; 162 main jet; neadle set in the middle. The motor is done resently, from botom to top, new! It starts very easy and botom-end power is fine, but from mid, it starts stuttering en topend is somer dies.

How do one check/test the powervalve?
What els can it be?

Please give me some pointers?  

 

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