Obviously this happens with the engine warm/choke off. Definitely an _Air/Fuel_ issue if it always stays smooth...(as in not running on one cylinder spadically). I might suggest checking the air intake system...maybe a carb boot not sealed....or even a possible vacuum leak ?
Others on the forum are able to assist you better than I.
hope this helps
'86 VN750 13,700 mi -Stock -Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust ! ...have a vulcan good day!