As in one of your previous posts I had mentioned what jetting we run in the FCR carbs, but that is in Australia. May not work overthere. Though you had mentioned that it had fixed it with that jetting back then, but I notice you have now come back in that post and said it isn't fixed.
You've messed around that much with that carby and nothing's working, maybe the flat spot has nothing to do with the carby or maybe the carby is internally rooted.

I had a car come to me just lately and the previous mechanic had rebuilt the holley carb 3 times, replaced the fuel pump twice, new distributor, new coil trying to resolve a flat spot issue which ended up being a simple vacuum leak.

Sometimes we have to think outside the box. What else can cause a flat spot in a Petrol (gasoline to you guys) engine? I think you will find a list that is pretty long.

I hope the flat spot you're describing isn't when snapping the throttle when the bike is stationary? You will never tune that out, you will, but your plug will turn black pretty quickly, should only ever test the carby bikes while riding them.

 

i probably am doing something wrong i will keep trying different things

 

okay so i took the bike on a ride ocemn needle 4th clip 160 main jet and 45 pilot if im slow on the throttle it works very good but if i punch the throttle below half throttle it bogs down for a second then accelerates good if im going too slow then it will bog and die im thinking accelerator timing is off or main jet is still too big

 

Accelerator pump should squirt just under the slide as it's coming up and for a minimum of 3 seconds. I rarely change the main jets on these bikes. We leave them factory and usually put a 48 or 50 pilot in it, then we adjust the mixture screw accordingly.
Can you stall the bike if you set the idle low and screw the idle mixture screw all the way in?
If you can't or it's making no difference to the idle of the bike then you have an air leak or your pilot jet is too small and your idle is up to high and it's drawing fuel from somewhere else to compensate.
There are many things that will cause a bog in low rev hard load acceleration. Poor spark or ignition component. An ignition system will flat spot if accelerated hard under load if it has a weak component. Obviously this opens up a whole heap of possibilities, so lets hope it's not that.
Lean condition is the most common on these bikes which is usually because the accelerator pump has failed or the pilot jet is too small or you have an air/vacuum leak.
Poor octane rating of fuel or old fuel will cause a bog under hard acceleration. (especially old ethanol fuel)
Blocked or over oiled air filter, partly blocked intake or even partially blocked exhaust.
Or as you're thinking, too rich. (Which also works hand in hand with poor spark)
With my experience on the rfs bikes, you usually have to be deadly rich before they will bog from running to fat unless the plug is very black and full of carbon.
If you put a fresh plug in on a rich rfs bike, you usually get 5 to 10 minutes of good running before it starts to bog as it starts to carbon up the plug. (This is of course if the ignition system is in good condition).
I would nearly go out on a limb here and say that you would almost need to see black smoke at low revs with a fresh spark plug for an rfs bike to be too rich to bog straight away.
I see heaps of riders sit and rev there rfs bikes and pluck the throttle hard which is only throwing way to much fuel in and blackening up the plug. The amount of fuel the fcr carb accelerator pump throws in is designed for a bike in motion.
There's nothing worse for an rfs than reving it stationary. (This is the case for many four stroke bikes actually).

 

so i went ahead and put a 155 main in it 45 pilot and the ocemn on 4th clip and it still has this issue when its at low rpm the bike will bog down and then accelerate normally i feel as if there is one little thing i am missing everything in the carb works valves are adjusted good spark no vacuum leaks im 100 percent sure at this point its simply just getting the right jets in the carb and to get rid of the bog

 

Have you ridden it around normally with your current jetting and pulled the plug? (Don't pull the plug after idling or reving stationary)
I personally have never had the jets that lean, but I have never worked on a big bore 400. I have done a couple 525 big bores (the 580) and the jetting was similar to the standard 450's and 525's. What really made us fatten them up a lot is if the exhuast was much larger or aftermarket.
Is the header pipe sealed and not leaking at the head? Is it the stock exhaust? Can you stall the bike with the mixture screw?
I personally would put a larger idle jet in (say a 50) and adjust the mixture screw by idle response. (Turn in until revs start to drop off, then back out a turn)