'81 carb problem...

[steve murdoch icoa #5322]

I am hoping for a confirmation of my carb problem diagnosis [i was just at the doctor].
I have an '81 that is running poorly. It had a slight stumble at around 3500 rpm that was cleared up with a couple tanks of Seafoam gas treatment.[turned out to be dirty gasoline]. A similar problem returned this spring so i decided to clean the carbs. Following Mike Nixons great manual i flushed, air compressed and quitar stringed my way through all the passages. Or so i thought.
The bike now has a stumble/rough running from idle all the way to 5500 rpm where it clears up and runs like a champ. I have to be ON the gas for it to run well. Any deceleration and it runs like 2 cylinders have cut out.
Having read a pile of entries in the Carb section, i figure it must be partially clogged slow jets causing the trouble?
I am hoping somebody will suggest a carb synch as a cure.Wishful thinking, i know.
It is an '81 with a stock air filter, 6-6 Pipemasters, and the fuel line diaphram has been bypassed. It ran pefectly last summer.
Thank you in advance for any thoughts/ideas.

[EMS]

It sounds like a slow jet problem. How did you set your air mixture screws?

[steve murdoch icoa #5322]

I am embarrassed to admit it Mike, but i did it the scientific way of 2-1/2 turns out and a plug colour check. A light tan colour and all of them VERY similar in shade.

[EMS]

No reason to be embarrased. I did the same thing. It is a good starting point. Biggest problem with these are the small O-rings and the washers. They sometimes remain stuck in the bore. If you think you lost them and add new ones, the position will be off.