Hi, I have weird problem. Once i start up the engine speedometer instantly shuts off. It works perfectly when i do not use motor. Does it happens with all digital speedometers? I tried with two of them, both had same problem. I think it happens because of vibration.
Some digital speedometers are more affected by
EMI/RFI from small engines than others. Some engines produce more EMI/RFI than others, as well.
I have seen speedometers work fine with one engine but not other one of the same type. It's almost always caused by the engine's magneto.
The windings aren't particularly consistent, and shielding is pretty much non-existent. If your digital is wireless, the problem may be exacerbated.
You can take several steps to get your speedometer working:
1) Isolate the speedometer from the frame the best you can. Since your engine is using the frame as a ground, it can cause some interference in a digital speedometer- wired or not.
Start by insulating the frame where the speedometer head mounts and also the fork where the pick-up mounts. If there are any cables, shield them from the frame.
2) Install a ferrite core noise suppressor on the plug wire. These are inexpensive and snap right on. It may be hit or miss whether it works well enough, but I've had good results.
3) Run a resistor version of a quality spark plug (small threaded cap). You may also need a plug boot that works with such a plug. Make sure it's good quality, I recommend NGK.
All of the above should get your digital speedometer working. I've been running digital speedos for over 20 years and have seen some weird behavior from them!
The analog needle speedometers just don't last on our bikes. Believe me, I've tried many. Digital all the way!