I know this is an old post, but I thought I would bring it back up with my review of my R&D power pump 2.
My ATC450R that is in my signature had this problem also when I was building it. It uses a 2005 CRF450R motor with a RMZ450 carb. It already had the safety wire tie mod done on the accelorator arm. I was told this is supposto fix this problem, but I am picky and I noticed the bog big time.
What happens is that the accelorator pump manually pumps fuel directly into the carb through and orfice in the the carb body. You can actually see it with the filter off as you apply throttle. The leak jet is what deteremines how much fuel is put through this opening. The larger the jet, the less fuel, the small the jet, the more fuel. As you mod stuff this becomes more evident and should be rejetted just as you rejet your main and pilot jets. You can change the leak jet out like is mentioned and wire the accelorator arm open so that it is always fully opened, but this still isnt really the "right way" to do this.
A company called R&D racing makes an accelerator pump cover that also has an adjustable leak jet circuit. I installed this and the difference is night and day, and the customer service is amazing.
There are other companies out there that make a similar product also such as Merge Racing and Boyseen.

Word!
Another good thing to do is cut the bottom metal stud on the diaphram that is inside the AccPump (if your model has room). That or install a crf450 diaphram. Gives it the full squirt.

With the R&D the instructions actually tell you to grind off that part on the diaphram. I did not have to do this apparently the RMZ already uses a shallower diaphram.
Heres a pic of it installed, I have some of when I was installing it but, but cannot find them right now.

just drill the diaphram on the acc pump cheap fix..Seen many apps bbIII has done on here and they work great

One thing I have noticed on my 06 yfz that has greatly reduced (but not eliminated) the bog is to address the idle fuel mixture. I installed a 45 pilot and an adjustable fuel mixture screw, 2.5 turns out on an 80 degree day (I only have a slip on pipe, k&n, and removed air box lid). This helps keep the engine going excessively lean when hitting the throttle too quickly. I know when my idle mixture is too lean, the quad will pop on a heavy decel. Adding a little more fuel to the idle mixture may help significantly, see what you think.

Yeah, my quad pops out the exhaust when I come off the throttle alot. I really noticed it especially this winter. I'm gonna pay attention to see if it is just a cold weather thing.

I need someone to hold my hand and help me fix this bog problem on mine..... any volunteers?

If the engine pops worse when it is cold, it is too lean. The cold, dense air requires the mixture to be richened up. Have you installed an adjustable fuel screw? I adjust mine every time I go out and ride. It makes that much difference. I'd be willing to help you out as much as I can. There is so much misinformation on other sites, it can make trying to understand a carburetor more difficult than what it really is. Simply put, determine which circuit you are dealing with, then make it leaner or richer. If you are at idle, then punch the throttle, then you are dealing with two circuits--idle circuit (which the pilot jet and fuel screw come into effect here) and the accelerator pump circuit (which is the pump and the leak jet). If, at idle, the engine is already at the lean limit and then the throttle is opened up quickly the accelerator pump has to overcompensate for this lean issue (which isn't good later on trying to set the needle and main). What I did was get the idle to be at the proper air/fuel mixture. I went ahead and zip tied/safety wired the accelerator pump linkage together, and checked the timing of the pump squirt. (I have this recorded under my seat in magic marker, I think I set it at 1.5 seconds. I'll have to check.) My yfz doesn't run PERFECT, but to gain that last little bit will require way too much work for what I am willing to do. I ran my quad on the dyno down at Little Sahara just to see some numbers and I was pleased.
The first thing I did was install the fuel screw, and change the pilot. If the fuel screw is set between 1 and about 3 turns out, then the pilot is correct. If the fuel screw needs to be closer to the full in position than one turn out, go smaller on the pilot (this would be going leaner.) If the fuel screw is turned out three turns and still needs to come out more, then change the pilot to one size larger (I think stock was 42). I have a 45 pilot and usually around 2 turns out on the fuel screw. I tend to think of the fuel screw as making the pilot somewhat adjustable (it helps me understand it a little better).
I honestly believe if the bog you are referring to comes into play from opening the throttle up quickly from an idle, then correcting the pilot and fuel screw will help tremendously. After correcting the pilot/fuel screw jetting and the bog still is unmanageable, then address the pump cover, linkage, leak jet, squirt timing, etc.
Be slow and methodical making changes on a carburetor. And please, document what changes are made (from what and to what, and what the weather/temperature is).

I rode GV Friday, a nice warm day and didn't notice anymore poping. So I believe it just runs lean in the cold. The bog is really the only complaint I have. I'd like to upgrade my exhaust/ air filter this year..... and make some adjustments then.

a dyno a is a pretty expensive means to jet if you using it to tune and for hp well untill i dyno passes me on a track its pointless lol..Your bike will also pop if its fat but it will pop with a black puff of smoke. I will second writing down where you start from and note what changes you made and what you changed to this will help you become a carb guru in no time!If you are going to start playing with your jetting for compensation of the notorious bog you will be sorry.Unless you do it through your diaphram you will be non stop messing with it because it will be off other places.you will want to jet one jet at a time dont change your clip position ,main and pilot at the same time.Depending on the throttle position where you notice your problem that is the area to play with and do it only.o to 1/4 is pilot.1/4 to 3/4 is needle and wide open only is main!