Hayter 10/30 wont run fast/operating speed?

Engine starts but will only idle. When throttle opened engine gets noisy, as if no silencer fitted, but doesn't increase revs. fuel supply checked, carb stripped & cleaned no obvious fault, spark plug replaced. Appears to blow fuel out of carb intake. Engine has only done about 5 hours work. Briggs & Stratton 10HP
BG, September 2012


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