How do I speed up a Merit Vision Sport?

The belt tension is fractionally too slack.

If it were the prop, you have vibration at high speeds/out of balance. Look at the back of both wheels. If one has oil around where the rearend meets the backing plate, bad axle bearings.

reduce the radius that causes the oscillation or slow down the motor speed

Sport Mode Indicator Lamp and Automatic Transmission Warning Lamp (STL)
The sport mode indicator lamp illuminates when the vehicle has been put into the sport mode by pressing the "S" button on the gear selector. When this lamp is illuminated the vehicle will have slightly firmer shifts and increased performance for part and full throttle situations.
This lamp will also flash when there may be a problem with the automatic transmission. The transmission control module (TCM) performs a continual self diagnosis of certain control functions. The lamp will flash only when an error is detected. The TCM will store in memory a current and/or history trouble code when a problem is detected. I'd have it checked out !

http://meritshealth.com/upfiles/profile01218471606.pdf (Service Manual)
having had a look i can not find one any were, you can disconnect the battery to do much the same as the reset button. if you can not find it any were you could easily put one on your self. they are dead cheap on ebay, hope that helps.

does the noice increase with incresed speed, if it is speed dependent it could be tire noise, wheel bearing noise

Aside from the very obvious connection that if you can't see well, it will clearly affect your sporting ability, vision is also connected to many inter related sport skills such as speed and accuracy.

If you see an eye specialist, they can advise you about getting the right kind of eye care for the sport you play. Either laser surgery, contact lenses that are suitable for you to maximize your playing skills.

u might be blowig too hard and cooling ur air down try slowing the fan down to a lower speed

this is a matter of knowing a little bit about your car, maybe a cv joint but I will gamble a little on the brake pads, when you apply the brakes they move inside the caliper and thats the noise you hear, try it on reverse, if it does the same thing check your blake pads.

There is a rotating handle to the right of the display panel that you need to turn clockwise to slow down and anitclockwise to speed up, this is the only speed control. Turn it all the way and it will start at the slowest speed about 4kph. Good luck