Hi, I have a 13/60 herald. This runs sweet as a nut up to about 50 mph, then once you start accelerating up to 60, it coughs and splutters like mad and loses power but still revs to a fashion. If stopped, the revs will go to max without any interference and all sounds good. I have changed the diaphragm, condenser, points and rotor arm. Fuel is all getting through ok as the reservoir near the engine is pushing it through fine. Any help would be appreciated. Thank you PS Have a new coil and dissy cap ordered.