Engine died would not start.. cleaned carb with commercial cleaner and changed plugs now it starts stays at low idle engine misses and stumbles when throttle to fast no increase in rpm. When I press down on carb linkage to front butterflys on carb the engine runs up to full speed but if I let go engine stumbles and throttle does not control rpm. Looks like throttle movement doesn't affect linkage to butterfly valve - will check if linkage broken?