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Buell Forum » Knowledge Vault (tech, parts, apparel, & accessories topics) » Electrical - Battery, Charg Sys, Lights, Switches, Sensors & Guages » '05 Blast Speedometer Issue « Previous Next »

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Magus10112
Posted on Monday, July 22, 2013 - 06:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Hey all, first post on this forum. Seems really nice (but a bit inactive).

Anyways, I'm having a problem with my blast... Started today. Only 3k miles on the Bike at the moment.

Speedometer basically shows double my current speed. For example if I'm going 35 (my perception) my speedo will show I'm going 60. Does this at all speeds, including above pegged-out speedometer.

Anyone ever run into this issue before or have any inclinations on a fix?
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Reepicheep
Posted on Monday, July 22, 2013 - 07:08 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Never had a blast, but that's a weird problem. The speedo sensor is a hall effect switch that puts out a square wave when a magnetic field is interrupted. So when a tooth passes the sensor, which is just mounted over one of the gears (5th gear final drive?) a square wave results.

I have no idea how that could double... Could be a speedo problem instead of a sensor problem. An o-scope would probably help you tell, if you can get one I'm willing hook up my Uly to a scope on that sensor output and post a waveform for 20 mph (praying the whole time I don't launch the bike out the back of the garage...)
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Magus10112
Posted on Monday, July 22, 2013 - 11:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

First off, thanks for the response.

The bikes so knew, I really don't want to replace the speedometer for 100$+ if I can help it, especially if that doesn't fix the problem.

The speedometers I've seen marketed just connect to a cable(?) so if the cable was the issue, a new speedometer wouldn't do anything for me. It's a problem.

I could probably get an o-scope, but I won't pretend I'd know how to use it and figure out what the problem is.
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Reepicheep
Posted on Tuesday, July 23, 2013 - 08:37 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Blast owners can keep me honest here, but I think the Blast uses the same speedo setup that the other Buells use, which is a hall effect sensor connected by three electrical wires. It is mounted in the crankcase. It creates a square wave that the speedo uses do derive speed.

It's magnetic, so it wouldn't hurt to pull off the sensor (a couple screws) and clean any swarf off of it. You could check the wiring while you are in there. It probably wont fix it, but your problem is so unusual and it won't take long, so maybe worth a try.
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