Eletrical is usualy the issue for something like that. It could be running lean - clogged jet or so. Check the fuel line first, it is the easiest. The gas tank should also have a little prefilter going to the pet-cock. Check the fuel filter, Make sure your not running old gas either.
At high RPMS, if you can, pull the choke half way out and see if it runs any better, if it does, you may be lean and need a larger main jet.
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