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exwifeschewtoy

how off is a stock speedo?

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I noticed in town today on two occasions that my speed was off when clocked by a mobile radar unit....I think 40mph on my dash it was showing 36-37. Are vfr's known to read higher than they are actually going? In addition to having a speedometer not correct the idea that I am giving away free miles is not acceptable. I am due for a chain and sproket because I noticed that portions of my chain is stretched which is making it harder to find an ideal chain adjustment.  If speed is off by as much as 10% then I want to choose a sproket that will make up for the difference as close as possible anyway.

thanks

Joel

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I do believe that all motorcycle speedos are off. Given that the tire has a round profile rather than flat like a car, it is impossible to have a consistant and accurate speed reading.  Your speed indicated will be one thing riding totally upright and another when corning or hitting the twisties. To change the gearing will not correct this for all your riding.  It is the nature of the beast. Just be aware of it and move on.  Or you could get yourself a GPS and rely on that for your precise speed.

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I have calculated, based on both road-side radar and a GPS, that my fifth gen speedos, all of them, consistently register as ~8% optimistic. YMMV

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It's a very common issue with most bike speedometers. 8-10% is the norm. However the odometer is spot on, even

if the speedometer is off. So if you change your speedometer reading by regearing, your odometer will then be off.

 

When I went to the 45-tooth rear sprocket I installed a bicycle computer that I set to the correct speed reading. And

a GPS will work too.

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I use the Speedo Healer V3 unit (bought used from a goldwing) to accurately represent my speedo. I need it to be accurate because I do enjoy riding the bike fast. It under-reports the mileage though, but it won't really matter because I don't plan to ever sell this VFR.

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My VFR is down a tooth on the front sprocket so it was off 15.7%. I got tired of doing the math in my head so installed a SpeedHealer yeah the mileage is now off 15.7 percent.   

  • Haha 1

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44 minutes ago, thepretender said:

My VFR is down a tooth on the front sprocket so it was off 15.7%.

 

Methinks your arithmetic is faulty. Your '02 VFR came with 16/43 gearing, so a 15 tooth sprocket changes the gearing only by ~6%.

How'd you come up with the 15.7% value?

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2 hours ago, Urbanengineer said:

I use the Speedo Healer V3 unit (bought used from a goldwing) to accurately represent my speedo. I need it to be accurate because I do enjoy riding the bike fast. It under-reports the mileage though, but it won't really matter because I don't plan to ever sell this VFR.

 Why would it under-report mileage if the speed is set accurate?

 

If you set the speedohealer to -99% it would yes I reckon.. :tongue:

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12 hours ago, Lorne said:

 

Methinks your arithmetic is faulty. Your '02 VFR came with 16/43 gearing, so a 15 tooth sprocket changes the gearing only by ~6%.

How'd you come up with the 15.7% value?

Used GPS (phone) to get real mph then use math to calculate from reported mph difference is 15.7%.

Nylon thingy on sensor is shot so for next couple of days getting 0 mph and 0 miles per gallon 😁

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13 hours ago, Lorne said:

 

Methinks your arithmetic is faulty. Your '02 VFR came with 16/43 gearing, so a 15 tooth sprocket changes the gearing only by ~6%.

How'd you come up with the 15.7% value?

If the mileage was already off to begin with, and you add some more it could add up to that much. I added 2 teeth at the rear and

mine is now off around 12-15%.

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13 hours ago, thepretender said:

Used GPS (phone) to get real mph then use math to calculate from reported mph difference is 15.7%.

Nylon thingy on sensor is shot so for next couple of days getting 0 mph and 0 miles per gallon 😁

 

Ah, now I see what you meant.

 

Btw, it simply isn't possible to have both an accurate speedo and an accurate odometer on 3rd, 5th, or 6th Gen VFRs. My examples all had speedos that read about 5-6% high while their odos were near spot on. (checking against mile markers keeps the mind occupied on long rides through the American west )

 

Btw, I assume most other Hondas are the same but can only comment on the ones I've owned.

 

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Every Honda, Suzuki, Kawasaki, and Yamaha I've ever owned all read high on the speedometer. The only bikes

I've ever owned that were on the money as far as speedometer/odometer readings were a '71 and '73 Triumph

Bonneville.

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