you say adjust the idle using the right screw do you mean the right carb or the idle adjusting screw on left carb on top
The right as in CORRECT screw. The idle adjuster on the top of the left-hand carb.
Yes you can adjust the mixture screws with the engine running. Just blip the throttle and let it settle after each adjustment.
Here is how to set the mixture without using a gas analyser.
"First, run the engine until it reaches normal working temperature, say 10 to 15 minutes, then switch off. Remove air cleaner for access. On each carb below the electro-magnetic cut-off valve is a mixture screw. Turn both in all the way, then back off each 2.1/2 turns. Now restart the engine still with the air cleaners off. Adjust both screws slowly in the SAME direction until the engine runs at about 750 rpm. Next, remove the right-hand magnetic cut-off valve live connecting wire, listening carefully to the drop in revs. Then reconnect. Do the same on the left-hand side, again noting the decrease in revs. If the rev drop is different, this proves the mixture is incorrect on one carb so adjust by small amounts both mixture screws until the speed drop is identical, with each magnetic cut-off valve wire removed in turn. This all requires patience and takes time to get correct but if is important and well worth the effort in the end.
For the final stage and with the engine running, concentrate on the left-hand carb, on the top of which you will find 2 screws. The right-hand one is the actual idle speed control which must be turned until the engine speeds up to around 900 rpm. Next, turn the smaller left-hand screw a little in both directions until the engine runs smoothest. If the carbs and the engine are all in fair condition, this should be as good as human hands and ears can expect without expensive special equipment. I must stress that this is only a very abridged and simplified description for home tuning and will not, of course, provide worn out carbs with a new lease of life. Even so, it is well worth while for, in 9 cases out of 10, the main problems we find with these twin carb engines is mal-adjustment of the carbs. Providing the above method is carefully followed, a fuel consumption of not less than 20 mpg should be obtained."
