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SM speedo gear on S?

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Has anyone tried installing an SM speedo gear onto an S to see if it makes the computer readout any more accurate?

Let me clarify: I'm talking about running the SM speedo with the 21"/18" dirts wheels and tires.

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EDIT - OH WAIT, yes, it makes it a bit more accurate but then the odo is off. I leave my SM drive on for both dirt and street.

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EDIT - OH WAIT, yes, it makes it a bit more accurate but then the odo is off. I leave my SM drive on for both dirt and street.

Well, the odometer is off now, isn't it? And it's off in the wrong direction. Since the speedo is reading high the odometer is clicking over more than it should and reading more miles than actually traveled. If my speedo and odometer are going to be off I'd rather them read low!

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The odometer on a stock bike is pretty accurate (within 1%), It is the speedo being off by 8% or so. There is nothing that can be done about it short of an aftermarket display.

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How it works:

<S cheezy TV music>

Drive cable enters the speedo and rotates a shutter wheel. A IR emitter/detector counts the pulses the shutter wheel makes as it rotates.. I beleive there are four windows on the shutter wheel. Each window is a certain distance traveled. These 'clicks' get added and become mileage. The clicks are also added, divided by time and become speed, Each time the epeed it displayed/updated, the count begins anew. In the code used to calculate, a deliberate 'fudge factor' (not fear factor) was used, upping the speed. Sort of like a twenty on a stack of ones. Looks good but it is smoke and mirrors.

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Yup, hard coded, deliberate error. I bought a second speedo, took it apart and attempted to see if it could be reprogrammed. Nope. I mean it could be done but for the amount of time it would take to reverse engineer it, the costs to buy and swap chips, I'd have to do a 1,000 or more speedos at $100.00 each to barely break even. I bought a Vapor instead.

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Yup, hard coded, deliberate error. I bought a second speedo, took it apart and attempted to see if it could be reprogrammed. Nope. I mean it could be done but for the amount of time it would take to reverse engineer it, the costs to buy and swap chips, I'd have to do a 1,000 or more speedos at $100.00 each to barely break even. I bought a Vapor instead.

I hear that! I'm considering a Vapor myself depending on which SM wheels I end up with.

Where does the Vapor pick up the signal for the odometer? Is something added to the hub?

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Yup, hard coded, deliberate error.

Yeah, I would imagine the magic triple digit achievable speed had a lot to do with it. I mean, who here hasn't told everybody their bike will do a hundy.

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I hear that! I'm considering a Vapor myself depending on which SM wheels I end up with.

Where does the Vapor pick up the signal for the odometer? Is something added to the hub?

The Vapor uses a reed switch setup. You mount a sensor to your fork and a magnetic bolt to your brake rotor. Every time the magnet passes the sensor, a 'click' is sent to the unit. You calibrate your unit using the actual tire circumference. Instead of using the Rotor mount bolt like Trail Tech suggests, I used a regular magnetic bolt that was included with the Vapor. I installed this in one of the 'lightening holes' on my SM rotor. I was able to then shim it slightly, bringing it closer to the sensor for more reliable reading and to not have to worry about using (fairly) flimsy magnetic rotor holding bolt, for peace of mind. I drilled and tapped my caliper mount to accept the sensor and ran the cable zip tied to the brake line. I then removed the stock speedo drive from the wheel, installed a oil seal and a spacer on its' place (same parts used on the rotor side) for a nice clean install.

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Yeah, I would imagine the magic triple digit achievable speed had a lot to do with it. I mean, who here hasn't told everything their bike will do a hundy.

LOL, mine will, though I had to modify the engine a tiny bit first.

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