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Discussion Starter · #1 ·
I changed my front sprocket recently to a -1 sprocket (13 i think) and today I wanted to check if the speedometer still is accurate. I didn't do this while I had the stock one, that's why I am asking if you experienced something similar with the stock oder modded sprockets.

The problem is:

If I drive with in the "city speed limits", around 30 - 60 kph the speedo is off by around 10% (driving 60 the gps showed 54)
Once I drove on the Autobahn with a 185 the gps showed 175! So only around 5% off... Is this normal?

Maybe yamaha does this on purpose so you have accurate numbers on the track at high speed and don't risk a ticket for speeding on the streets.

I used to diffrent apps. Both showed the same.
 

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No fancy conspiracy, just several variances adding up. At slow speeds, the 1% error on your GPS app(pretty standard accuracy for consumer based trackers) is a more significant difference than at autobahn speeds.

Think of it this way with numbers, every second the GPS pins where you are. This could be off by a few meters if the signal strength from the satellite isn't great.

At 30km/hr you cover about 8m/s. Being off by even 1m will seriously affect your GPS speed accuracy. At 150km/hr, you cover 40m/s. Being off by a meter is significantly less impactful.
 

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Discussion Starter · #3 ·
No fancy conspiracy, just several variances adding up. At slow speeds, the 1% error on your GPS app(pretty standard accuracy for consumer based trackers) is a more significant difference than at autobahn speeds.

Think of it this way with numbers, every second the GPS pins where you are. This could be off by a few meters if the signal strength from the satellite isn't great.

At 30km/hr you cover about 8m/s. Being off by even 1m will seriously affect your GPS speed accuracy. At 150km/hr, you cover 40m/s. Being off by a meter is significantly less impactful.
Well that makes sense! Thank you very much ^^
 

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14 -> 13 is a 7% change, so it should be off by quite a bit now, as it read ~3% high in the first place (well mine did). Your speedo should be off by about 10% now. Yeah it's hard to get accurate results with the speedo and a normal gps. I taped my phone running a gps mph app next to the speedo, so I could see real time changes around 35, 65, and 100 to see what the error was like.
 

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Discussion Starter · #5 ·
14 -> 13 is a 7% change, so it should be off by quite a bit now, as it read ~3% high in the first place (well mine did). Your speedo should be off by about 10% now. Yeah it's hard to get accurate results with the speedo and a normal gps. I taped my phone running a gps mph app next to the speedo, so I could see real time changes around 35, 65, and 100 to see what the error was like.
Yes, that's what i did with the phone. Would you recommend buying a speedo healer?

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Sorry if i sound stupid or something but aren't speedometer cable linked to the front tyres, hence using no. of rotation of the front wheel to determine the speed? how does changing sprocket size affect speedometer accuracy?
 

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Discussion Starter · #7 ·
Sorry if i sound stupid or something but aren't speedometer cable linked to the front tyres, hence using no. of rotation of the front wheel to determine the speed? how does changing sprocket size affect speedometer accuracy?
Actually a friend of mine told me the same... But in all the forums they said it will change the speedo. I think they read the speed inside the gearbox, for what i understand


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I've checked the R3 service manual, on page 5-73 it states the speed sensor is mounted to the engine crankcase breather cover and is connected to the ECU, which I think is what VectorMt03 has stated.
 
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Yes, that's what i did with the phone. Would you recommend buying a speedo healer?

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I have a spare healtech speedohealer (+FZ6R wire/harness), but unfortunately I can't find a place where you could buy just the R3 cable / harness. Seems like they are always sold as pairs.
 

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I've checked the R3 service manual, on page 5-73 it states the speed sensor is mounted to the engine crankcase breather cover and is connected to the ECU, which I think is what VectorMt03 has stated.
Just to verify:

Since the speed sensor is in the crank case, does that mean I can swap to an aftermarket rear sprocket and still maintain speedometer accuracy?

Thank you in advance.
 

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Just to verify:

Since the speed sensor is in the crank case, does that mean I can swap to an aftermarket rear sprocket and still maintain speedometer accuracy?

Thank you in advance.
Any changes to sprocket tooth counts will change the speedometer...

Speed-o-healer is $100, I know the paper math says its a 10% difference but I had to program the speed-o-healer for 14% when I went -1 on the front.
 

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Just to verify:

Since the speed sensor is in the crank case, does that mean I can swap to an aftermarket rear sprocket and still maintain speedometer accuracy?

Thank you in advance.
Any changes to sprocket tooth counts will change the speedometer...

Speed-o-healer is $100, I know the paper math says its a 10% difference but I had to program the speed-o-healer for 14% when I went -1 on the front.
Thank you for the reply.

I gave this some thought after I posted and this certainly makes sense.
 
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