Strange running problem

[billythegrape]

77 GL1000
No engine mods. Carbs have been rebuilt. New coils, wires, caps, resistor. New honda fuel filter. Air shut off has been rebuilt. All hoses are new. Valves adjusted last year. Gas tank electrolized in July. New fuel pump. Timing belt and water pump have been done, as has thermostat. Dyna ignition. Straight pipe exhaust.

The bike runs and idles great mornings (60-65 degrees F) until after about 5 miles. At this point, it sputters and wants to die at idle only. It'll start back every time, but sometimes I have to give it a little throttle. This sputtering is intermittent but enough to be worrisome.

On afternoons going home (80-100 degrees F), it does the opposite. After 5 miles or so, the idle wants to rise to 2000-2500 RPM. Runs great otherwise. I counteract this by closing the throttle at the grip and locking it with the throttle stop.

Could this be leaking float needles? The plugs read normal; hard to tell with ethanol fuel these days.

[dingdong]

Were the carbs synced after rebuild? You might want to re-check. A sync should be the last thing done after all the other tuning procedures are complete.

[billythegrape]

I synced them. They were within 1-2psi of one another.