4Th Gen Hesitation At 4K

I am running out of Ideas trying to solve  a hesitation problem with my '96.

It idles fine and comes off choke very quickly.  In neutral, not under load it revs easily.

But when I accelerate under load, once I get to about 4k, there is hesitation as if  it is only running on 2-3 cylinders.

I started with a dose of Seafoam when that didn't solve the problem, I opened up the carbs.

They looked clean, but I made sure by spraying carb cleaner and compressed air through all the passages.  The jets were clean.

Next I replaced the fuel filter,

bypassed the fuel pump,

Left the gas cap open in case the vent was clogged,

replaced the plugs,

checked the resistance of the coils,

verified the timing advance,

synced the carbs,

Used an unlit propane torch to check for vacuum leaks,

Checked the exhaust can for obstructions,

Since I live and ride above 6000 ft elevation, it usually runs a little rich, so I  leaned out the idle,

and then removed the washer under the jet needle.

All with little to no change.  Adding choke while accelerating had no effect

Any thoughts,  could it be the coils?

any ideas how to check them under load?

But when I accelerate under load, once I get to about 4k, there is hesitation as if  it is only running on 2-3 cylinders.

This!!  You should be only under 4k in first gear, sometimes second in the local suburbs. After that, keep the revs up. its not a V twin.  What your doing above is lugging it. Stop it. 

--- Your not the first....

But when I accelerate under load, once I get to about 4k, there is hesitation as if  it is only running on 2-3 cylinders.

This!!  You should be only under 4k in first gear, sometimes second in the local suburbs. After that, keep the revs up. its not a V twin.  What your doing above is lugging it. Stop it. 

--- Your not the first....

it does this in first gear from 4k to at least 8k and did not do this in the past.

Does it hesitate in each gear?

Does it hesitate in each gear?

In my test rides since I first noticed the issue don't think I have tried  past 3rd.  Perhaps surging is a better description.  When I roll on the throttle at about 4k  it feels like 1 or 2 cylinders are not firing. 

Does it hesitate in each gear?

I guess I hit post before I answered that.  It hesitates/surges in multiple gears, not just 1st, but I don't think that I have tried all 6.

is it jetted?  Notched needles?  If it is, this is your issue.  That rev range in needle territory.  Either drop the clip one on the needle, or raise it.

Have you tried 'Ethanol Free Gas' ?? If it is available near you give it a try. Tried for months to find gremlins at lower RPMs  on my '97 tried a tank of ethanol free gas was like magic. I wont use anything else she runs so good on 'natural gas'. Good luck!