What blue lights?
Donating Member
Just got a GPS unit last night so ofcourse I had to go for a bit of fun on my lunch break today. Held speed at 130 mph for about 5 sec. and then came back down to semi-legal speeds. Once I got back to work I checked the high speed log and it said only 111 mph.

I know that all speedo's are off from the factory, question is does this difference seem a bit much or is it about right? I know the GPS is good ( I work on it in military ) so I'm not questioning that, just the differential amount.
I find my speedo to be about 10 kmph out starting at about 120 (so that's about 6 mph out). Check the refresh rate set on your GPS.. mine refreshes every 1 second I believe, maybe yours is set higher than the 5 seconds you mention, or you lost signal for a short time.
With stock gears my Busa was off about 7mph @ 70mph! So, I'd say your in the ball park for speedometer error......... Got a yellow box now, problem gone.
They are off about 6-7 percent. I put a 42t sprocket on and it was off by about 12 percent. I installed a speedo healer last Thurs. It was very painless. I printed out a picture of exactly how it is supposed be hooked up ( I did a search and found the picture). Now it is right on the money. Not bad for 66 smackaroos.

7.3 percent off with stock gearing. GPS I am sure is right on but top speed may not have been monitored long enough. It should have but? Is your gearing stock? Next run just set your GPS and compare the running speed at 65 and 85mph you will be able to tell the percent of error.