I would check that the throttle cables are not snagging or pulling tight when you turn the handlebars,as you say it seems alright when riding, presumably with the bars in a straight line. Another thing that could make the revs rise is a weak mixture caused by an air leak, might be worth checking the rubber inlet manifold for splits or perishes, personally wouldn't have thought that would make it rev to 10k, but worth a check.
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