save me from going bald, i have a 1986 yamaha D125 with 4500 true miles, when it runs it is ok, at other times it will start with the first kick but the engine will not rev up and stays at tickover speed. I have cleaned the tank,fuel lines ,stripped the carb replaced the float and the needle,main jet as well but i still have the same problem, is it engine/electrical fault. Any help would keep my barber in business.
Try loosening the petrol cap, if it runs a treat then the hole in the top that lets air in and therefore petrol out the bottom is blocked starving the bike of petrol. If you cant clean it out drill a hole in the cap and fit a piece of fish tank tubing into it and ty-rap the other end to the handlebars
GSX750 Ratfighter / SR125 Rat / GSX600F / Beamish250 / Honda70 Rat