Switched power source for Dyna

My apologies if this has been asked already but when installing a new Dyna ignition in a 1975 Z1 instructions say to connect red wires to existing switched power wire. Any recommendations on which wire to use? This is a new harness and I’m not excited about cutting wires. Would you use the plastic splice connector that came with it? 

I use a bullet connector to connect to the Y/R double connector going to the coils.
 

Those blue "scotchlock" connectors are the devils work - never use them unless you want mysterious electrical issues 

I agree with both of the above.  I have a Z1B with a dyna.  I used the brown double bullet connecter near the headlight to connect mine.

It's best to connect to the coil feed so the dyna can be switched off when not in use. Also the green 3 OHM coils should be connected in this way. Both items are power hogs and turning the kill switch off will prevent power drain and protect the coils when working on the electricals. I also installed a relay so the coils get their power direct from the battery. That way making pig tails off the relay provides space to hook everything up while not cutting into the wiring loom.   

I may be wrong on this but my understanding is that the only time power reaches the coils is when the dyna system "pulses" as the magnet passes by the pickup.  This provides a short power burst to the primary side of the coils, creating an electromagnetic field that induces a current in the secondary winding, sending a spark to the plugs.  The engine has to be running for this to occur.  If there is a constant DC voltage at the coils there is no field created hence no spark to the plugs.  This is why I use the brown hot wire to supply power to the Dyna.  

If it is left on for an extended period of time without being used it can be burned out. 

hardrockminer wrote:

I may be wrong on this but my understanding is that the only time power reaches the coils is when the dyna system "pulses" as the magnet passes by the pickup.  This provides a short power burst to the primary side of the coils, creating an electromagnetic field that induces a current in the secondary winding, sending a spark to the plugs.  The engine has to be running for this to occur.  If there is a constant DC voltage at the coils there is no field created hence no spark to the plugs.  This is why I use the brown hot wire to supply power to the Dyna.  

HRM I believe you are "half right". In a points ignition the period where the points are closed is called the dwell period, whilst the points are closed current flows through the coil and when the ground is broken (points open) the magnetic field in the coil collapses which is what causes the spark. With an ignition such as a Dyna when the magnet passes (however I do believe there is a delay in switching the ground to the coil back on so the dwell is shorter), the ground is broken causing the spark. What you are referring to "a short burst" is true "CDI" ignition. The coil has a constant ground and during the "dwell" period a capacitor in the CDI unit charges then when triggered gives a burst of approx 300v to the positive side of the coil - the spark is generated as that energy burst expires and the magnetic field in the coil collapses

Thank you for that explanation Wookie.  I was actually thinking of a Dyna pickup when I wrote that.  Not to get too nerdy here but am I correct that the coils only see voltage when the rotor passes the magnet?

The coils receive voltage all the time through the red / yellow live. The green and black from the pick ups trigger the coil discharge to the plugs when the magnet passes the pick up.
Thats why it's not a good idea to leave the ignition on without the engine running as the coils will overheat and melt the insulation of the windings. 

hardrockminer wrote:

Thank you for that explanation Wookie.  I was actually thinking of a Dyna pickup when I wrote that.  Not to get too nerdy here but am I correct that the coils only see voltage when the rotor passes the magnet?

As Warren says, the coils see a positive supply when the ign/kill switch is on. During the "dwell period" the coils also see ground (charge up period) which is when current flows, when the points open or magnet passes the pick up the ground is broken, when the ground is "broken" the magnetic field around the primary winding collapses - this is the point at which the HT voltage is induced in the secondary winding and the spark is produced

If using that bucket double female Brown apparently You only relied on the ignition (Key) to shut the bike off. Brown is still "switched" but you don't have the RH handlebar switch for a quick shut down. I would re-route. Unless your knob for RH is messed-up.