Do you know how fast or how far you are going?

[DMPLATT]

I'm not sure about older motorcycles.
However, newer motorcycles do in fact have built in error in the speedo. I don't fully understand why.
However, the ZZR's are well known to have about 10% error. Mine is just about exactly that. At 65MPh, the GPS shows 59MPH.
Many Police Speed guns that I have passed show the same results.
My friend on a 2005 Busa, rode with me to a ZZR rally in Georgia. I had a hand held GPS and his Busa is also right at 10% off.

My GS though, I don't recall that being off much at all.

 

[bwringer]

Speedos are deliberately built overly optimistic, likely due to a tangled knot of liability issues. The usual 5% - 10% error you see on new bikes is just ridiculous, IMHO, but some nervous Nelly lawyer somewhere thinks it has to be that way. At least on newer bikes with electronics, you can usually buy a little widget to plug in to correct this.

On a bike that's 25 - 30 years old, isn't it enough of a miracle that it's moving? Ancient mechanical devices like GS speedometers and tachometers are only haphazardly accurate. Each one is slightly different and special in its own way, like a snowflake.

 

[lurch12_2000]

Speedos are deliberately built overly optimistic, likely due to a tangled knot of liability issues. The usual 5% - 10% error you see on new bikes is just ridiculous, IMHO, but some nervous Nelly lawyer somewhere thinks it has to be that way. At least on newer bikes with electronics, you can usually buy a little widget to plug in to correct this.

On a bike that's 25 - 30 years old, isn't it enough of a miracle that it's moving? Ancient mechanical devices like GS speedometers and tachometers are only haphazardly accurate. Each one is slightly different and special in its own way, like a snowflake.

Now..now, I expect my bike to do more than just move. Maybe I shouldn't push my "snowflake" to 100mph, but I was just curious how far off the GS speedos were back then.
There are 2 things I NEED to find out. Locate a speed trap sign that flashes your speed and go through it :-s10-20 times to get numbers for my speedo variance. The other was to get weighed in at the local recycling plant to clear up the discrepancies in weight specs from manuals, internet sites and original brochures. The stupid things I waste my time on.........I'll report back to the forum as long as I don't get arrested or crushed for scrap in the process!:shock: