crankshaft sensor going.
check your timing & up your idle a little
sounds like the timing is off
Look for a vacuum leak.
If the engine idles and revs up okay in neutral, it is likely the torque converter clutch lock up solenoid.
Replace the plug wires
Starts hard then it rough idles for a short time then smooths out but when you give it gas it miss fires and bucks and does not smooth out.
Perhaps throttle plate is stuck open - try to free with a screwdriver
i have a 92 buick riviera that putters and chuggs when i accelarate but idles great
Year, make and model would help.
It needs adjusted it is still engaging. just like when it is running in Neutral and you put it in first gear it idles down more so than typical of a bike doesnt it ?
mine is doin the same thing
your tcc could be faulty, assuming its an auto. faulty neutral switch maybe