Speedometer not accurate

I've suspected that my speedometer was a little off for a while. I tested it tonight with my wife following me in the car and it's about 5mph off.

If my speedometer reads 60mph I'm really going 55mph. I don't see anything in my manual about how to adjust this. Where do I start?

mine's off by about 5 mph too. I think it may be further off the faster I go.

Stock tire size? A bigger tire will affect the speedometer.

i think its fairly common for the speedometer to read fast on bikes but yeah tire size will affect it. I wouldn't worry about it if its not too bad.

There's no adjustment. They read high.

Good to know this isn't that unusual. As far as tire size I know the rear is stock because I replaced it and made sure it was stock. I'll have to double check the front. If it isn't stock it's not far off.

Were these off when they were new or is this something that happens to 30+ year old speedos?

Would it effect the odometer too?

A couple of observations.
#1 You are assuming that the car is accurate.
#2 Even new bike speedometers read fast. I believe that it is a subtle safety measure.
#3 Yes it will add miles faster than actually accumulated. In your case it seems to be about a 9% error.
#4 About the only adjustment that I know of is to change front tire size. Keep in mind that with a new tire you may be able to get it right temporarily. As your tire wears it gets smaller in diameter, and guess what? You're right back in the same boat.

I personally wouldn't worry too much about a 9% speedo error. It might keep you from getting a speeding ticket.

You can change the worm gear in the speedo drive. It is a pain in the ass but doable. I calibrate my speedo with a GPS. That is the most accurate way short of asking a Cop to time you with RADAR.

A 10% error seems to be pretty typical of Japanese bikes. I have read other remedies, none of which have I tried--

1- Determine error at an indicated speed (say 70mph). Disassemble the speedometer and move the needle on the shaft enough to read correctly at the given speed. This, of course, means that there will be grater error at speeds below 70, and less at speeds above 70. Also, Kawasaki speedometers are a pain in the b**t to dis- and reassemble.

2- Send the instrument to a company that re-calibrates speedometers. $$$$$$$$$$

3- Duct tape a GPS receiver on top of the old speedo and drive like you stole it!

Ok, sounds like I shouldn't sweat this.

The car is nearly brand new, so yeah I assumed it was right (or at least close). What made me notice in the first place was that when I was going 65 on the bike I was getting passed a lot more often than when I'm going 65 in my car. That makes sense if I was actually only going 60 on the bike.

Thanks!

Here's something you may want to check. If you have measured mile markers on a highway nearby, or some other way to accurately determine an exact highway distance in miles, measure that same distance using the odometer on your bike. The odds are good that your bike's odometer will be pretty accurate if the diameter of your front tire is close to that of the bike's original equipment. If this is the case but your speedometer is not accurate the problem lies in the gauge. There are businesses that specialize in fine tuning speedometers, but most folks just live with it and run a bit faster than the indicated speed to compensate. Ed

You can also use a GPS to check how accurate your speedometer is. Probably the easiest and most accurate way to do it. The odometer error which may be 3 or 4 percent at most can be verified with a GPS too.