Earlier, I drained the float bowls, removed all the vaccuum and fuel lines, and flushed the carb with Berryman's B12 aersol carb cleaner. Then I ran the engine with a high concentration of the cleaner in the gas, and sprayed it into every available orofice while it "ran". This bike will barely run with the airbox off., but you can force it. Then the bike sat for a few months, while it rained, and I did other things. About 6 weeks ago.. I faked together all the tubes, set the air box on top... and ran the bike a few minutes.
Today, I made sure all the tubes were in place and properly secured, replaced the airbox and filter, and fired it up. After it idled awhile.. I backed it out of the motorworkshop...let it warm up, put on my gear and took it for a 20 minute ride. GOOD NEWS ! the flat spot in the throttle response between 3600 and 4000 is nearly gone.. and no longer troublesome. Previously I worked pretty hard to get the carbs as well balance as I could. So, next step will be to finish the other "garage queen" service.. new fork and brake fluids, control and chassis lube, and more riding to break in the brand new tires. Back in the motorcycle riding business !