Mystery Electrical Part

I have no idea that purpose this serves -- I'm still tracing lines but it has bee removed completely from the blue bike and is still intact in the red bike

Update & Solution

Mystery is Solved - This is called a Zener Diode or a Heat Sink - the problem is that bulbs will blow from the current variations, so they put this in to regulate the voltage- what I have read is that these do not last long at all - at roughly $30 each they recommend a Voltage regulator instead. Of course my Electrical was previously converted to a 12V system so I will have to source out a part - but the normal regualtor would have been a 6 Volt 12 Amp Voltage Regulator. Another Term for the Voltage regulator is "Clipper Diode"

The root of the problem is a Faulty Coil that is spitting out too much juice - Ill have to see if this becomes a problem later