Burble / Unsteady at 4-5000RPM

[VT_BluYamaha54]

Need some help with a problem on my (stock) '04 Warrior. 11K+ miles, runs well except for an annoying burble/hunting around 4-5KRPM. Looking back in my notebook, this has actually been a problem since new but it seldom occurs since I am not usually running much in that rpm range. Carbs are sync'ed and mixture screws are set at about 1.5 turns from seated. I am thinking of moving the needle clips up one slot (to lean it out) since if I move the choke when it is in this rpm range, it worsens.

Anyone have any other thoughts?

 

[grader]

check the diaphrams in the tops of each carb. be carefull not to loose the small "o" ring under each cap. check for damage to rubber and fitment in carb. possible you might have one or more floats not set right, as you say it has happened since new. before you take anything apart, with airbox removed reach in to each carb and lift slide with your finger and let it drop. do this to all 4 carbs and note the resistance and how long they take to drop when you let go. they should all be the same, not sticky or hanging up. if one is different start there.

 

[VT_BluYamaha54]

check the diaphrams in the tops of each carb. be carefull not to loose the small "o" ring under each cap. check for damage to rubber and fitment in carb. possible you might have one or more floats not set right, as you say it has happened since new. before you take anything apart, with airbox removed reach in to each carb and lift slide with your finger and let it drop. do this to all 4 carbs and note the resistance and how long they take to drop when you let go. they should all be the same, not sticky or hanging up. if one is different start there.

Grader - thanks for the reply; sorry to be awhile responding. I checked drop of the slides and they were all equal. I have had the carbs off and apart a few times so I don't suspect floats but I should double check them to be absolutely positive.

I went ahead and dropped the needles/moved the clips up one notch and inspected coils + plugs. Nothing out of the ordinary - Yammi replaced all 4 coils awhile back.
The issue is still there so I guess I will keep digging. I had set the idle mixture needles at about 1.25-1.5 turns out awhile ago. Maybe go back to factory (2.0) and start from there(?) as maybe it is a transition issue from low to mid-range?? Frustrating because it is just within that RPM that it is lousy -