who was it that posted about the speedo on e-bay?

[motorpsycho]

a few days ago there was a post about speedometers. someone posted a link to a digital, battery powered speedo on e-bay for $2.94 (from hong kong).
i'm just wondering if they got it to work (whoever it was said that he bought 3 of them).
well, i bought one and i did get it to work...until i started my motor.
as soon as i start the motor, the speedo wigs out, resets itself, and then all the numbers lock on 8888888.
it works fine without the motor running, and i tried several different things to isolate it from touching anything on my bike. i even went as far as taking it completely off my bike and holding the entire thing in my hand. sitting on my bike i can fire the motor up with the speedo in my hand, and it does the same thing as when it is attached to the bike. (resets, and all #'s lock on 888888).

i was just wondering if the other guy got his to work, and if he had the same problem that i am having.
since this thing is battery powered, and is totally encased in plastic, i can not figure out why it messes up when i start the motor. I even went as far as totally disconnecting my cdi box from the frame thinking that it is sending current out to the frame.
for some reason, it seems like my entire frame is "charged" when the motor is running. i had the same problem when trying to hook up a headlight to the white wire....but that's a whole different story.
all of my wiring has been soldered, sealed with heat shrink, and wrapped in plastic convolluted tubing. no bare wires are touching anything, and my motor is isolated from the frame with rubber pads.
i can not figure out what is causing this.

 

[motorbikemike45]

The magneto must be sending strong "radio" type electro magnetic waves out. I'm not sure how to isolate a device from such signals. Any radio savy types might be able to help with this problem

 

[Shadeslay]

Normally a shielded plug wire will do the trick.

 

[Porkchop]

Is the speedo a wireless unit ? I haven't read of problems with wired units. I have a wired Schwinn and have had no problems.

 

[motorpsycho]

well as far as being wireless...yes and no.
it is battery powered, and the battery is housed inside the speedo head.
the sensor that leads to the front wheel is wired to the speedo head and there is a magnetic pickup on the spokes.
even if i remove the entire unit from the bike and just hold it in my hands while i'm on the bike with the motor running, it will re-set itself and lock up.

 

[Dilly Bar Rob]

Yes a shielded plug wire should solve this. Even just an automotive grade (resistor) plug wire may be enough to cut the RF interference to a reasonable amount. There is a reason why they don't use copper wires (anymore) to the spark plugs in cars....


When I lived in europe one of our neighbours drove an old "Trabant" car - 2 cylinder aircooled 2 stroke, 600cc, fiberglass body, points ignition with 2 coils and unshielded COPPER wires to the plugs... If you were watching TV off of an antenna & he was out driving the picture would go crazy a LONG time before he drove by. Electric spark is THE ultimate RF interference creator.

 

[Al.Fisherman]

It was I that posted about the speedometers on E-Bay. I have the same problem as you mention. I'm working to solve the issue with a resistor plug wire as mentioned. The plug wire that comes in our kits are in fact wire. Might only be about 5 strands the thickness of a hair but wire none the less.

 

[motorpsycho]

i have a bunch of extra resistor plug wire left over from when i made the plug wires on my 55 pontiac. how do i get the resistor plug wire hooked up to the cdi box?

 

[Shadeslay]

Just screw the wire on to the cdi. There's a screw in the center, so it just threads on.

 

[motorpsycho]

ok, that was easy. the way the cdi looked, it looked like the wire was molded into it and sealed.
i unscrewed the wire and put on a nice peice of red accell 8 mm superstock resistor plug wire in place of the old wire. it took me about 10 minutes to do it.
i'll see if that makes a difference tomorrow....it's too late at night to run the motor right now