I have a 1984 gl1200a that will not go over 70 miles per hour it is stuck at 4000 rpm at full throttle. I dont understand because when parked the bike can rev way past 4000 rpm. can any one help????
Hector, see if it will go over 4000 RPM in 4th gear? If so, you have either a fuel flow problem like a failing fuel pump or a plugging fuel filter, or a restriction at the tank petcock, or plugging screens in the carb inlet needles.. OR, you could have dragging brakes (jack the bike up & check that).. OR, you have an air flow problem to the carbs (look for a plugged air cleaner).. OR, you have misadjusted throttle cables not allowing full carb opening (twist the throttle wide open with the engine off & look to see that the carbs are opening all the way).
You could also have other problems like malfunctioning ignition box, or failing pulse generators, or low coil voltage, or failing coils but the most likely cause is either mis-adjusted throttle cables or lack of fuel flow. Maybe try a new fuel filter first as that is the usual cause of low top speed & make sure you have good fuel flow from the tank petcock.
If you can pin it down to one of the above systems post back & we can help you repair that area.