The steering geometry of a motorcycle affects it's handling. Altering the preload front and rear can alter the feel of the bike and its ability to turn by raising or lowering the back and front of the bike changes the rake and trail speeding up or slowing down the steering. These improvements would probably be minimal and would be offset by a wallowy or to bumpy a ride. Suspension is designed to keep the wheels in contact with the road without allowing the bumps and imperfections affect the motorcycle and not to tune the frame geometry. Some bikes have ride height adjusters fitted to the rear shocks and fewer have adjustable yolks these adjustments allow you to adjust the bike to behave how you want. So before you alter suspension settings such as damping, preload etc. the geometry should be setup so that the bike works as you want it. If you are adjusting an existing bike the easiest changes can be made to the rake and trail by raising and lowering the front and back of the bike by dropping the forks through the yolks for example. Wheelbase and offset usually need new parts to make any significant changes but bikes like the 916 Ducati are adjustable for ride height and fork offset and wheelbase.

What You Can Adjust

REAR RIDE HEIGHT

Increasing ride height reduces the rake at the steering head and reduces the trail. On a Firestorm fitting a 6mm spacer under the rear shock mounting would reduce the trail from 24.89 degrees to 24.28, the trail from 97mm to 93.5mm and the wheelbase would be 1427mm. Which compares with Foggys 95 race 916 at 24.5 degrees 100mm trail and a wheel base of 1428mm

FORK DECK HEIGHT

Increasing the deck height (the amount the front forks stand above the top yolk) also decreases the rake at the steering head and the trail by similar amounts unfortunately ground clearance is reduced and care need to be taken to make sure the forks don't hit the bottom yolk on full compression. A maximum value of 10mm is the most that is possible

FORK OFFSET

Decreasing the fork offset only affects the trail so a 5mm decrease in offset increases trail by 5mm (see the diagram above)and a 5mm increase in offset decreases the trail by 5mm.

WHEELBASE

You can shorten the wheelbase by shortening the chain or increasing the number of teeth on the rear sprocket and moving the back wheel forwards this will certainly make the bike more likely to wheelie and a little easier to turn.

GEOMETRY

RAKE

The angle of the forks raked back from vertical. It is possible to have zero rake e.g. vertical forks but the bike is likely to steer like a shopping trolley. The forks wouldn't work properly either with the brakes on they would flex backwards instead of compressing and anything but the smallest of bumps would have the same effect. The rake of the forks directly effects the trail the smaller the angle the shorter the trail and the larger the angle the larger the trail.

TRAIL

The difference between where the front tyre touches the floor and where a line drawn through the steering head would touch the floor. The amount of trail determines how easily the bike changes direction. Lots of trail makes the bike stable and more effort is needed to change direction bikes with large rake angles like Harleys are stable in a straight line but need effort to turn because of the large trail. Less trail makes bikes more unstable and more likely to tankslap but they turn quickly so most racebikes have short trail values.

WHEELBASE

This is the distance measured between the front and rear wheel spindles. A Long wheelbase makes a bike more stable less likely to wheelie and slower to turn hence most drag bikes have longer wheelbase so the don't flip over backwards or tankslap the rider to death. A short wheelbase quickens steering but makes the bike more prone to wheelies and stoppies so a compromise is reached where steering is quick but the power of the bike can be used without to many wheelies.