A little pack fires, coughs and twitching. And yes, everything else is check like air leakage, throttle balance, ignition timing...
Which way, cw or ccw, I should turn air mixture adjust screw if I want it lean way?

It's not recommended to turn the TB's air screws, if that is what you are referring to, unless you have a way to measure the air flowing through all four of the throttle bodies simultaneously. The 'richness' of the motor is controlled by the small screw under the plug on the top of the airbox, right hand side. I recommend some way to measure the mixture using an exhaust gas analyser. Also, the ignition timing is best done with a dynamic timing light, hopefully an adjustable one, and also the timing mark isn't 'fixed' as it's dependent upon where it was set originally. You would have to measure whether it's advanced or retarded. The factory settings and how they arrive at them are convoluted. Here is a link to one person's way of measuring and then setting it.

http://skylands.ibmwr.org/tom/tech/k100_timing.html

Others will, I'm sure, have some good advice for you on where to look, but an air leak is likely, or perhaps a coil is about to go tits up. Have you looked closely for fine cracking of the air intake rubbers? Good luck with it.

ccw will make it leaner, as you open the bypass of the AMM further which measures the air passing through to adjust the fuel quantity.



But TWB has good advise! Make sure everything else is OK as this screw normally doesn't shift.

Hi there, here
http://skylands.ibmwr.org/tom/tech/co-setting.html
is a way to do it without an exhaust gas analyser.
Best regards
JAP