Speedometer correction

How do you correct the inaccuracy of the speedometer?

Ride faster... or slower :-)

I've no problem at all with my speedometer reading a few MPH lower than my actual road speed as displayed when using sat nav/GPS.

It's an advantage in some of our English counties that are festooned with fixed speed cameras, or on roads where hidden speed camera vans are lurking.

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Looking at my post again I was obviously having one of senior moments and meant higher, not lower.

As per the original OP's question, you don't. On bikes with electronic speedometers you can find speedometer correctors. Speed Healer is one that worked well for a friend on his Goldwing. They list compatibility with the Silverwing Scooter on their site. With one of these you can recalibrate your speedometer to GPS accuracy. They cost a bit over $100US or 79EU. Besides calibrating your speedometer they allow one to switch the readout from MPH to KPH and record your highest speed.

https://www.healtech-electronics.com/products/sh/

Thanks, that is what I was looking for, just forgot the name.

What year bike do you have? What rear tire?
I have a 2013. IRC tire. Speedo is right on with GPS. 1 mph at worst.

Was looking to correct the speedo on my 2009 Yamaha V-Star 950. Rear tire is a 180/60/16. Error is right at 5 mph.

OK Ride on. Cruiser. Put 21,000 miles on a 1999 Honda Magna. Good bike V4 750. Needed some RPM's
to pull top speed though. 135 topped out maybe. Passed 12 cars and a motorhome once, 2 lane NY.
RT. 8 coming home from MX race Unidilla. DUMB.

My 650 Savage had the same error, going from 140 / 80 / 15 to 140 / 90 /15 corrected that, so probably going from a 60 to a 70 would correct yours
You will lose some acceleration, and it may take a slightly harder push on the bar to drop it into a curve after that (did on the savage) whether that's acceptable to you or not is your choice

Increasing the diameter or mass of the front wheel will affect handling slightly. A larger or heavier front wheel will develop more gyroscopic force which resists turning. It will also increase leaning effort. Most bikes have a low speed where the bike wants to 'fall' into a turn, i.e. you don't have to push down on the inside grip. Go a little faster and it takes pressure on the inside grip to initiate and hold a turn. On my scooter the change occurs slightly above 25mph. This is caused by the gyroscopic force of the front wheel. The bikes suspension geometry will effect the phenomenon but it's common to every motorcycle and scooter I've ever ridden. It's related to the speed where direct steering turns to counter steering.
If you've never really understood counter steering try it on a bicycle. It's very obvious on a bicycle that at very slow speeds you turn the handle bar into the turn, but a bit more speed requires the rider to turn the bar away from the turn. Most people never notice this on a bicycle. It's the same on all two wheeled vehicles.