Bing Carb sync using a Twin Max

1. Valves need to be adjusted and bike needs to be well warmed up.
Well warmed up means 20 minutes or so of riding at reasonable speed.
If you are having problems with a racing hot idle, 90% of the time it is
due to NOT WARMING UP THE BIKE before adjusting the carbs.

2 You need to start with a little slack in the throttle cables. When you
pull the cable up in the ferrules/stops on the top of the carbs you need a
gap on each side, say 1/16" scant or close. Even better is observing when the throttle levers starts to move when twisting the throttle. They both need to move at the same time and have a gap when you pull the cables up. This will be fine tuned in the last step, but if you don't have a gap you may not have room to adjust things later and there may not be sufficient freeplay for the throttles to reach the stop.

3. Hook up the twin max, turn it on and increase sensitivity to max and
adjust the needle to center. You can then turn down the sensitivity back
down all or part way and turn unit off.

4. Start bike, turn twinmax on and adjust idle using throttle stops so it
idles at rpm you want and is in sync side to side. Older airheads 900 to
1000rpm, newer usually 1000-1100 rpm. The needle points to the side that has LESS vacuum. That is, it points to the side that has the throttle opened up more.

5.Now adjust the idle jet control screw to best idle. The Bing manual will tell
you the factory setting or starting place. Usually 1/2 to 5/8 turn out. Then turn the idle jet screw in until engine wants to die and then out until it wants to die. Some put it in middle of  these two points, some adjust it to best idle speed or sweet spot in between the two points. Either way works ok. I use best idle. (If idle jet doesn't do anything, the idle circuit is plugged or there is an airleak. If this is the case I first try and pull the idle screw and squirt some carb cleaner in there. That often helps.)

6. Then you have to go back to the throttle stops and readjust them to
correct idle and in sync. They may have been thrown off by changing
idle jet adjust. But unless you've made major adjustments of the idle jet it is likely that very little readjustment of the throttle stops is necessary.

7. The last step is adjust the sync JUST off idle. If your idle is at 1050 rpm slowly bring the throttle just off idle, observe the range from 1050 to 1150 rpm.. In this step any off-idle hesitation should be eliminated along with making sure the cables are pulling at the same time and evenly. This adjustment is done by using the threaded 10mm nuts on the cables at carbs.. This is where giving yourself some room earlier comes into play. You may only need to adjust one side or the other. Giving a slight tug to the cable and seeing which way the twinmax needle moves can help you *determine* if you need to make a cable shorter or longer. Again you want them in sync just off the idle..

8. That's it! Do take care not to overheat the engine. If it takes more
than 5-6 minutes, I'd use fans or take the bike on a cooling off ride and
then continue.

Jeff Trapp with much help from David Paulus