Well the pull start or electronic start will have nothing to do with how your car idles. There should be an idle adjustment screw on the carb. Usually below the carb opening (air filter housing), adjust it so its leaves a minimum 1 mm opening, or if you can adjust it the lowest just before the engine dies.

Now which gears are moving fast?. If its just the clutchbell spinning and not the spur gear, then you have a clutch problem. If both clutch bell and spur gear are turning, then there is something wrong with the drivetrain. Check also if your brakes are set up correctly.