ACVs on Keihin carbs?

[Black Knight]

One of my bikes is a Honda CX400 (don't laugh) and the stock Keihin VB carbs are fitted with ACV (air cut off valves) the purpose of which is to supply extra fuel on decel to prevent popping.I have been retuning the carbs after cleaning and with the LH one I have no problems,adjusting the pilot screw effects the revs and fully closed will kill the LH pot.However,the RH one is the problem,no matter which way you turn the pilot screw,there is no change in the rev range and screwed fully in has no effect.I understand that a faulty ACV can cause this problem.Has anyone had experience in this area?Is a faulty ACV the only cause of my problem?I have examined the diaphragm and it does not seem to be holed,the small o-ring is also in place.-I understand that by blocking off the o-ring orifice on both carbs, thereby isolating the ACV feature,even though it would then sound like an HD on decel-after all it is a V-twin,-could eliminate the problem I am having.Seriously though I would like some guidance,could it be something else that is causing this.-Thanks

[Black Knight]

Contacted the USA based World Guru on Keihin VB carbs who gave me a list of items to check-It all came down to the diaphragm in the ACV,which while it looked OK other than a slight distortion,obviously enough to create a leak.A new diaphragm sees the bike running sweetly again,as it should.

[Ocean1]

Don't you just hate it when it turns out to be something you've already checked?

Been a common enough experience for me that for years now I've just replaced diaphragms on the slightest suspicion.

[Black Knight]

So will I in the future,its just a bastard to get to the RH ACV on this particular bike without splitting the carbs, and easy to catch the diaphragm edge on assembly.I am getting very good at it though.