Maybe Pliers
Disclaimer- As with any mechanical adjustment, if done improperly this procedure could be
cause your bike to malfunction and could cause severe injury in the event of a crash.  If you
are at all unsure of your ability to perform this procedure correctly, PLEASE do not attempt to
do so.
All the fine tuning should be done at the throttle, the adjusters at the carbs
are for major changes, and if you need those it is a safe bet that something
major is wrong, like the carbs are installed at the wrong angle or something
similar.  Start by pulling back the rubber boots.
What you are aiming for is 2-4mm or free travel.  In other words, you
should be able to move the twistgrip back and forth 2-4mm without
engaging the throttle blades.  To adjust for this, screw the cable in or out
depending on if they are tight or loose.  If they are too tight, screw them in
towards the grip.  If they are loose, screw them away from the grip.
You should be watching the cables down below at the same time.  You
want to move the grip back and forth with the free play you have and see
if the cables have slack in them.  If you twist the grip and cables
immediately move (by move I mean slide up or down to actuate the
throttle blades, rather than just wiggle as if they had slack), they are too
tight.  You want to twist the grip, see some slack in one or both of the
cables, then twist a little more and have it actuate.
I set up this masking tape with marks to illustrate.  You'll
see that at rest, the mark on the bar lines up with a mark
on the grip.  Three millimeters away is another mark.
When I twist the grip and take out the slack (just
before it actuates the cable), the other mark lines
up.  That means I have 3mm of free travel.
Now twist the grip all the way and
check for binding.  Then let go and
see that it springs back into position.
This just illustrates what you should look for as far as
slack down below.  At rest, the cable should have
slack, otherwise the idle will be too high (it's already
partly opening the throttle blades).
At rest, you should be able to push up
on the cable to see that it is not
pulling the blades open already.
Once finished, simply lock the locknuts down and pull the rubber
boots over.  Start the bike up and check that it does not change the
idle when you turn the bars.  If so, the cable are too tight.  Alos check
that the RPM's don't hang after you release the grip.  If it checks out,
you're done!
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Motor Holding, S.p.A., all other content on this website is copyright 2006, Monster Man Productions.

Does your bike have a hair trigger?  Does it buck and lurch through turns because of
abrupt response?  Does the idle fluctuate when you turn the bars?  Does the idle hang
up?  Is it hard to twist the throttle?  Does it not spring back when you let it go?  Have
you changed carbs recently?  Well, if any of the preceeding were true, it's likely that  
you need to adjust your throttle cables.  Perhaps they were installed or adjusted wrong
before, or they have stretched over time, or any number of reasons.  Whatever the
case, it is an easy adjustment.
Then loosen the two lock nuts.  Pliers may be
needed for this, but they should just be finger tight.