Speedo's and gas engines...Help !!

It's driving me nuts..... I'm on my second speedo, the electronic one with the magnet, and i'm starting to think that they are not compadible with these engines running !! Always cutting out at a certain speed and sometimes going blank. I tryed a new battery and a different location, with no luck. I'm hoping sombody may be having the same problem and found a solution. Must have something to do with harmonics from the magneto Or ???????

same problem

I was thinking of looking for an older style that's mechanically linked to the front hub. Probably hard to find now a days.........

im told it is emf, dont put electronics near the motor,

Simply put, they don't work very well due to the unsheilded ignition on our bicycle motors. You can get the cable drive speedos from a lot of sources on the web, including ebay.

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If it ain't broke, and you mess with it long enough, it will be.

If is is EMF, one could do what carmakers do for vital sensors that measure engine rpm very nearly exactly the same way our bicycle computers do... Twist the wire. About two twists per inch is more than enough. (Maybe even less, say one twist per 3/4") Then wrap it in a continuos spiral of foil along with a thin-gauge uninsulated wire and ground it to the frame. When the magnetic wave from the ignition hits the twisted pair wire, the voltage it induces into the wires will now be opposite each other, cancelling them out. Also, the sheilding will carry away some of it before reaches the wire. Note: the shielding isn't bulk related. You don't need more than a single thin layer (of course each spiral will overlap onto the previous one.) and it doesn't help any more to was it up around the wire, as the fashion police will stop you. Take a long strip, say, 8 feet or so, cut into a 2 inch strip. Lay it on the floor with the uninsulated wire taped every few spots to keep it from wandering, alongside your twisted wire computer pickup just a bit off of parallel. Roll the wire into the foil at a relatively shallow angle...say 30 degrees, overlapping each wrap about half the strip width, or an inch or so. After all wrapped, spiral on a layer of electrical tape to prevent foil tearing. Make sure it's grounded to frame using the uninsulated wire!

It's a lot of work, and twisting alone may be enough. If not, go for the foil.

Two things I have done that seem to have alleviated some of the problems are:

Something similar to mentioned above but a little simpler. Take whatever excess wire you have on the speedo wire and fold it back on itself as shown in the picture. It helps cancel out some of the EMI.

The other thing I have done is use a shielded plug wire, basically standard automotive wire and boot.

Seems to have solved the problem.

Attached Thumbnails

 

A resistor plug will help too.

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If it ain't broke, and you mess with it long enough, it will be.

Had to go to work and came home to all this great info !!!!! Thanks guys. I will post my trial and errors !!!!!

All of you are right However if you happen to live near an airport and can ask an aircraft mechanic he might just have some used electronic shield cable
laying around. It wraps around cable like a spring. It kills emf by about 60-80%. If that don't work a mechanical speedo is the way to go. (unless your bikes Haunted) Couldn't help it. Ride safe All