NEWTRONIC ELECTRONIC IGNITION INSTALLATION

This photo shows everything that came from Newtronics when I purchased my Ignition Kit.

Unlike the custom-fit kits, this one included three rotors. The middle one was an example to show how to cut the rotor. The right one was not cut at the top but had been cut at the bottom to fit on the advance mechanism for the TX750. It had also been fitted with a bushing since the shaft that drives the XS650 points mechanism is larger than the TX750 points shaft. This is the one used for my installation. Newtronic included a third totally untouched blank rotor (left one) "just in case".

This shows the front view of the old points assembly and the front view of the Newtronics unit. Fortunately for TX750 owners, the backing plate for the XS650 and TX750 must be the same size. One of the few parts that interchange between the two models are the points. They sure give you plenty of wire (way too much in my opinion).

This is the rear view of the same two assemblies. The Newtronic unit works with light sensors. When the sensor for one of the cylinders is uncovered by the cutout in the rotor, that plug fires.

This is the old points advance mechanism with the points cam in place.

The points cam has been removed and the rotor is ready to be mounted. You can see the thin metal bushing used to make the XS650 rotor work with the TX750 engine.

The uncut rotor has now been mounted on the advance mechanism. Notice that the counterweights fit into the two slits cut at the bottom of the rotor and the pin sticks through the extra notch cut in one of the slits.

The Newtronics backing plate is placed in the opening where the old points assembly was removed. Make sure the adjusting screws that holds down the backing plate are in the middle adjustment position, so you can tweek timing one way or another if your cut in the next step is a little off. The Newtronic backing plate is not as thick as the metal TX750 points backing plate, so the standard round washer will not contact the Newtronic plate. Replace the flat washer with a split lock washer. The tang on the lock washer will grip the backing plate and keep it from moving. You may have to grind off two sides of the lock washer to allow it to fit in the tight clearances. As you can see, the generator cover has been removed to rebuild the electric starter as well as install the Newtronic unit.

The "fun" part is making the cutout on the rotor at the proper spot. You should set the timing mark at the proper spot, then insert the backing plate and uncut rotor as an assembly. You will have to remove one screw from each light assembly and twist them to allow the rotor to fit at the proper spot between the gaps of each light assembly. Scribe a mark on the rotor at the middle of one of the sensor lights. Remove the rotor and backing plate and cut out at least 90 but less than 180 degrees of the rotor behind the mark you scribed. Remember the rotor turns counter-clockwise, so the cutout should be clockwise of the scribed mark. Use the supplied shims, if necessary, to make sure the rotor is aligned vertically halfway between the contact "eyes" so that the components do not physically touch each other. It's not really as hard as it sounds.

The Newtronic unit requires a "black box" to monitor the sensor lights and fire the plugs. The "black box" has sticky tape on the back to hold it in place. I wondered how long it would take moisture and vibration to shake it loose. Finding a suitable spot to mount this "black box" turned out to be a real nightmare since almost every cubic inch of space where you would want to mount it is already utilized. The XS650 instructions said to mount it to the inside of the left side cover. My brother came up with the idea of strapping it to the battery using the standard heavy-duty TX750 strap. It just fits under the left side cover and the grounding point as well as a hot lead from the ignition switch are very convenient.

Here is a closeup of the final ignition installation before reinstalling the generator cover. You should split the rectangular rubber grommet off the old points assembly and place it on the Newtronic wire assembly to seal the ignition cavity. The grommet that comes with it is round to fit the XS650 cavity. You can see the hold-down lock washers that replaced the original flat washers.

The wiring for the Newtronic unit is much longer than really needed when installing it on the TX750 as you can see for yourself.

Here is a closeup of the final ignition installation with the generator cover and associated wiring in place. You need to set the static ignition timing as per the instructions titled Setting Ignition Timing found on the Routine Maintenance Page.

Small cable ties should be wrapped around the wiring to hold it together as an assembly and make a neater installation.

The excessive wiring should be coiled and held together with cable ties.

A. Blue ground wire from black box should go here B. Red/white hot wire from black box should tap into red/white wire here C. Coiled wiring should be stuffed in front of battery here