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Speedometer Gremlin

  • Thread starter Thread starter csgoh
  • Start date Start date
C

csgoh

Guest
Hi everyone. First and foremost, I want to thank this website as it has provided me with so much valuable information on how to build my bike and of course, the inspiration is priceless.

here goes:

I have purchased a Daytona Velona speedometer which requires a digital pulse input for speed sensing. Purchase a passive speed sensor (the one that works without a magnet. Has 3 wires (positive for power, ground and pulse output). Connected everything up:
1. Speed sensor connected near the wheel and within 3mm from the disc brake plate bolts
2. Pulse sensor wire output to speedometer

and powered up the speedometer. I have an issue of huge disturbance from revving the engine causing the speedometer backlight to flicker and registering 0-40kmph speed even though im stationary.

On the move, the speedo just cant register constant speed and keep jumping all over the place and not showing any accurate speed at all. Its basically an ornament now.

The tachometer (same brand and model) next to it is perfectly fine and not experiencing any flickering of the LED backlight.

I checked all wires and my bike is producing 13.7V of power to the meter (as the meter has a volt sensor inside).

I have included a video to show the issue and I wonder if there is anything I can do cause I tried all sorts including using resistors between speed sensor wire to speedo, resistor between power to speed sensor.

http://www.youtube.com/watch?v=RXi9KAf1k6o

Any help would be great as I would really want this to work.

Thanks in advance!
 
I have no knowledge of the instrument, but what you are describing is a loose connection, somewhere in the system.

I would revisit the wires and check each connector as one being just a but less than perfect will allow it so succumb to vibration .

Another possibility is that there may have been dirt in there during assembly that prevented the perfect electrical contact.

I had that happen on a brand new car...the dealership tried several times to find the problem, and failed, so I had to play with it at home. There was dirt between the ground cable and the engine block. It left the connection snug, but not tight, so the contact was intermittent.
 
One possibility is interference coming from the secondary side of the ignition system. (The coils, spark plugs, and the wires in between.) Check to make sure you have resistors either in your spark plugs or spark plug boots.

Tell me which bike you have along with the part numbers on your spark plugs and I can help you see if this is indeed the issue.
 
Thanks for the super fast response. My bike is a Gs550tx 1981. I'm using NGK B8ES spark plugs with standard NGK plug boots which I doubt have resistors as they look like just hollow plastic with direct connection to the coil cables. Coils are standard original Coils.
 
Going to do some cleaning to the wires this weekend but I doubt that's the case cause I did a total rewiring to the bike recently as I rebuild it. The issue with the speedo has been there previously before this new wiring and its the same with the brand new from scratch wiring. Also have the coil relay mod in there done. Bike running on Dyna ignition. Runs very well and performance is really great especially with the recent pod filters and rejetted carbs. Will share the rejetting experience on the forum for others as I noticed some are struggling with pod filters especially the cheapo ones. My pods are USD 16 for 4!....never thought it will work
 
If it's not caused by electromagnetic interference, or isn't the result of a loose connection, then logically it has to be a defective speedo.
 
I actually got a replacement for the speedo as I thought the earlier one was faulty. Replaced the speed sensor as well. Is there any way I can prevent the electrical inteference from the spark plugs or coils?

Will wearing an aluminum hat on my head help?

Serious note...any suggestions will be much appreciated
 
csgoh said:
I actually got a replacement for the speedo as I thought the earlier one was faulty. Replaced the speed sensor as well. Is there any way I can prevent the electrical inteference from the spark plugs or coils?

Will wearing an aluminum hat on my head help?

Serious note...any suggestions will be much appreciated
Click to expand...

I had a similar situation on a tachometer a couple of years ago. I solved the erratic operation by using "shielded" cable and grounding the shield at only one end. Good luck, Paul
 
Thanks Paul.

Would you mind elaborate slightly. What type of shielded cables did you use. And how do you ground the shielded cables?
 
hi guys, will changing to resistor plug caps help with the situation as I realized my plug caps are non resistor based
 
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