The error is based upon the tire circumference. So if yo uwere tryin gto correct for the proper speed you would have to find what you are actually dooing and then adjust accordingly by going to a different profile or even a different size tire of the same profile...Curt loves the math...he can get into it really deep...I could if I wasn't so lazy...if you take it to a speedo place they will tell you what you are doing with the tires on it already and nyou can mark the speedometer, after they give you the report or you can figure out what size tires you need and go back and see if you have it right. There was just a big article in one of the mags about spedos being off by a margin and how they were allowed to do it...USUALLY you are going slower than you think you are because the speedo registers faster than the actual speeed...so you could get taller tires/larger tires to make up the difference and be closer than what it is out of the factory/off the showroom floor.
I'm too lazy. I bought a Sigma bike speedometer which is doubling as my watch. It was always a pain to figure out what time it was cause I had to take my glove off to do so. That project is taking a backburner until the rest of the bike is rolling again though.
Mine is about 5mph off around 50mph. It reads too high. The law regarding speedometers (for OEMs) requires that if the speedometer is inaccurate, it MUST read too high. So most OEMs build them with a margin of error on the high side, so you're almost always going to read faster then you're actually going. The best thing to do is get a friend to go along side you and check it at a few different speeds.
A forum community dedicated to Kawasaki Motorcycle owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, maintenance, off-road, touring, street bikes, and more!