EMI interference

[stobby]

hey guys this is my first post.. woot!

I know I should be putting this post in the "noob" section because i just joined but I've been reading these forums long enough and pretty well know these motorised bikes from the inside out now. also i know there is a thread for my topic but my case is a bit different.

anyway, i recently purchased a digital speedometer and the EMI leakage (electromagnetic interference) from the spark plug wire is causing it to reset. i have experimented moving the CDI unit to the back of the bicycle with no luck, and I have found that it only resets when I touch the computer with the metal contacts coming from the sensor. so I think the interference is getting into the speedo cable.

I have 3 ferrite core chokes I believe that is the name, and i was wondering if they would be effective and if so do I put them on the spark plug lead or on the speedometer cable? I would prefer if I didn't have to go and buy anything i have already spent over $700 on this build. Its a 66cc china girl with a SBP shift kit. thank you in advance for anybody's help.

And also G-day from down under

 

[atombikes]

hey guys this is my first post.. woot!

I know I should be putting this post in the "noob" section because i just joined but I've been reading these forums long enough and pretty well know these motorised bikes from the inside out now. also i know there is a thread for my topic but my case is a bit different.

anyway, i recently purchased a digital speedometer and the EMI leakage (electromagnetic interference) from the spark plug wire is causing it to reset. i have experimented moving the CDI unit to the back of the bicycle with no luck, and I have found that it only resets when I touch the computer with the metal contacts coming from the sensor. so I think the interference is getting into the speedo cable.

I have 3 ferrite core chokes I believe that is the name, and i was wondering if they would be effective and if so do I put them on the spark plug lead or on the speedometer cable? I would prefer if I didn't have to go and buy anything i have already spent over $700 on this build. Its a 66cc china girl with a SBP shift kit. thank you in advance for anybody's help.

And also G-day from down under

Are the wires run parallel to each other? Of so, separate them as much as possible.

 

[The_Aleman]

Isolate the speedometer cable the best you can and snap one of the ferrite cores on the spark plug lead. That should take care of it.

If not, you may need to upgrade the spark plug and lead to something with "quieter" output.

 

[2door]

Although I'm a firm believer in metallic core ignition wire and non-resistor plugs, Al's advice has worked for many with little to no performance loss.
The high voltage leads used in today's cars and motorcycles was designed to eliminate electronic interference with delicate electronic devices such as computers, cruise controls, GPS navigation systems etc. Resistance wire was first introduced in the 60s when FM radios became common in cars. The older, solid metallic or copper ignition wires interfered with radio reception so a fix was needed. Today resistance wire is standard on all cars and most other motor vehicles.

The reduction in RF, radio frequency, or if you prefer, EMI, is significant so it will probably take care of your speedometer problems. Also the advice about keeping the speedo wires away from metal or engine related items, clutch cable, kill switch wiring is sound. The more seperation you can get, the better.
Good luck and let us know the results.

Tom