Bar Risers Sportbikes have a more forward riding position to purposely place the center of your body weight further towards the front wheel to better balance the bike and consequently improve handling. But for street riding it isn't the most comfortable position.
I installed Helibars on a 916 mainly to provide a more comfortable straight-up sitting position and to help solve a problem with numb fingers caused by handlebar vibration. However, after making this change I have mixed feelings about the new riding position. I prefer the previous handlebar position for more aggressive riding but I like the more comfortable neck position and my wrists don’t get as sore with the Helibars. Nevertheless, during certain riding conditions the angle of the bars just don’t feel right to me. I may change back or get a different product.
If I was to do it again I’d buy bar risers with some range of adjustment. The Helibars can be slid down the forks and rotated front-to-back but always keep their less-exteme tip down angle. I’d recommend instead a riser bar similar to that sold by Cycle Cat that are highly adjustable, but expensive.
http://cyclecat.com/home.htm I know that some riders have moved/modified their stock bars to raise the bar ends but this also sets the handlebars at an arbitrary downward angle that I find to be weird.
Numb Fingers Solution Numb fingers when riding a motorcycle is a common problem. The fact of the matter is that when you apply engine vibration to the nerves in your hand, the nerves go tingly and fall asleep. The amount of vibration and frequency is different for different motorcycles and at different speeds.
If you ride a sportbike the problem is compounded by a riding position that puts more weight on your hands. The weight of your upper body transmitted through your hands to the grips causes compression of the palmer cutaneous branch of the median nerve. This nerve compression temporarily impedes peripheral nerve conduction, causing numbness. Further, the more weight you put on the grips the better the transfer of the vibration to your hands, also producing numbness.
The solution (in order of cost):
(1) Change your grip more often and loosen your grip somewhat. We grip the handlebars tightly in order to maintain the throttle position and our body position. Unfortunately the tighter the grip the better the transfer of the vibration to our hands. Since it’s harder to vary your throttle hand position you probably have noticed that this hand is most affected by numbness.
(2) Use foam grips ($5 grips from a bicycle shop work very well). You can lessen vibration by isolating yourself and/or the bars from the vibration source by positioning a cushion (low frequency spring) along the path of vibration (foam between your hands and the bars) and/or use something to isolate the bars (i.e. rubber mounts) or the engine (i.e. softer motor mounts) from the rest of the bike at high frequencies. You can also try new riding gloves with thicker leather or gel padding on the palms... every bit will help. Use different gloves if your fingertips touch the ends of your glove fingers while riding causing any vibration to get transmitted directly to the nerves in your fingers.
(3) Add weight to the handlebars - at the ends - LOTS of it. The handlebar is actually responding to the engine's vibrations and will vibrate in harmony (resonate) at certain engine RPM. You can change the resonant frequency of the handlebars so that the bars do not respond to the engine vibration at say cruising speeds (shorter stiffer bars will tend to cause the high amplitude vibration to shift to higher speeds, longer or weighted bars will tend to cause high amplitude vibration to shift to lower speeds). Some manufacturers include weighted bar-ends as part of the design.
Weighted bar-ends are added mass that will lower the resonant frequency of the bar so it vibrates less strongly but does not eliminate all vibration. In many cases, that's enough. You simply change the resonance to a frequency that the bike rarely generates or to a RPM that has less effect on the nerves in your hand. Shifting the resonant frequency is intended to reduce the strength (amplitude) of the vibration at your normal cruising RPM.
I went to a dive shop and paid £3.00 for a 3 lb. lead belt weight (wheel balance weights and lead shot mixed with epoxy would work too), cut it up, hammered it into shape and shoved/wedged it in the handlebar. It’s got to be in there tight to work, closer to the free-end works best. The lead piece in each of my handle bars is about 5 in X 1/2 in.
Those lighter dinky bar-ends and Barsnake things they sell in bike shops aren't going to help as much. Placing rubber caulk inside the handlebars as some have suggested is unlikely to have much of an effect (beyond added mass) in damping vibration.
(4) Install bar risers to provide a more straight up sitting position that takes your weight off your hands.
After adding foam grips, handlebar lead and Helibars, the numbness stopped for me altogether. Before these changes my throttle hand would go to sleep to the point I was afraid that I wouldn't be able to use my front brake in an emergency.
The problem is that our nerves are just in the wrong place for motorcycle riding. Darwinian evolution will solve this eventually. So, start with the foam grips and then the lead weights. In the meantime, while riding, get rid of the numbness more quickly by momentarily tapping your fingertips hard against your thigh to get the feeling back.