If you own a classic British twin — or triple — and ride it with any regularity, you really owe it to yourself to consider an ignition upgrade. While the stock Lucas ignition system used on just about every non-magneto fired Brit twin from the early 1960s to the mid-1970s can work just fine, it requires constant attention, including points cleaning, gapping and resetting timing, to keep functioning at its best. And even then it can be an uphill battle; Lucas mechanical advance units are notoriously prone to wear and sticking at full advance, causing a high idle at stop lights and generally poor performance.
The answer to all this is to fit an aftermarket electronic ignition system. Using an electronic pickup and with no moving parts other than a rotor or trigger wheel, electronic ignition systems have been the norm for decades now, and have proven to supply years and years of reliable sparking.
The Tri-Spark system
For this How-To, we turned to well known Norton specialists Colorado Norton Works (coloradonortonworks.com), who are also the U.S. distributor for Tri-Spark Digital Electronic Ignition from Australia. We also tapped into CNW’s extensive experience with Tri-Spark (they fit all their custom Nortons with Tri-Spark ignition systems) by ordering up their custom single-coil conversion kit. Although the kit adds a not inconsiderable $152.95 to the $329.95 Tri-Spark system, we can tell you from experience that if you want simplicity allied with reliable starting, you’ll never regret spending the extra dosh.
Our subject bike was a basically stock 1973 Norton 850. Installation was straight-forward, taking no more than a few hours, and you don’t need to be a high-level tech to carry out this conversion. If you can use a crimping tool and follow directions, you should be able to undertake this How-To. The system is well thought out and nicely executed, making tuning a breeze; we found that static timing was all we needed, as running timing was spot on when we checked it with a timing light. And once it’s set, chances are you’ll never adjust your timing again.
The best part was finally firing up our Commando. It’s now one of the easiest starting, nicest running Commandos we’ve ever had the pleasure of riding. Although a properly tuned Commando should start easily enough, our bike now starts first kick every time — and runs like the proverbial scalded cat. Don’t believe us? See our video at MotorcycleClassics.com/norton-commando-start
Stock ignition includes a points plate, mechanical advance unit, condenser pack, ballast resistor and two coils.
CNW's replacement system uses a single coil, a self-contained electronic ignition unit and rotor, and new wires.
The first step is to remove the ignition cover on the right-hand or timing side of the engine. The cover is to the right of the “Norton” name cast into the timing cover. Simply remove the two screws holding it in place.
Here’s the points plate with its two sets of ignition points, one for each cylinder. Clip the two wires, remove the two “pillar” bolts at 1 and 7 o’clock and remove the points plate.
Removing the points plate exposes the Lucas centrifugal ignition advance unit, which is famous for sticking fully advanced, causing a high idle. You won’t miss it when it’s gone.
Remove the bolt securing the advance unit, noting the threads exposed at the outer end of the advance unit. Thread a 5/16 x 24 bolt 1 inch into the advance unit, then tap the bolt with a hammer from the side to free the advance unit from its tapered seat on the camshaft.
Here’s what you’re left with; a cavity waiting to be filled with the new ignition rotor.
Next, crimp the supplied bullet connectors to the stock ignition wires. You can do this at any time prior to finally connecting the new Tri-Spark unit.
Next, remove the inspection cover at the left front of the primary case. Put the transmission in third or fourth gear and turn the engine over using the rear wheel until the timing marks line up at 28 degrees before top dead center.
Loosely install the Tri-Spark ignition unit, centered on the pillar bolts as shown. Note the mark on the ignition unit at about the 4 o’clock position. This should line up roughly with the access hole for the ignition wires.
Make a mark on the timing cover corresponding to the one on the Tri-Spark, then remove the Tri-Spark. Install the rotor with its two magnets inline with the mark you made and roughly perpendicular to the pillar bolt holes, as shown.
Fully tighten the Allen head rotor bolt and check that the rotor is at least 2mm below the ignition unit’s mounting face using the supplied straight edge, as shown.
Loosely install the Tri-Spark, centered on the pillar bolts with the red ground wire eyelet secured by the lower bolt. Connect the ignition wires, which are color-coded.
We replaced the stock coils with a single, dual-outlet coil kit from Colorado Norton Works. This photo shows the stock dual coil setup.
Remove the old coils, followed by the stock ignition ballast resistor and condenser pack, which mount between the coils on the frame plate the coils attach to. Install the CNW coil and bracket as shown, bolting it at the original coil mounts.
Crimp the supplied bullet connectors to the ignition wires and secure the black/white lead to the right terminal, the stock red ground wire to the left terminal and the black/yellow lead (shown disconnected here) to the blue/white hot lead from the factory wiring harness.
Next, hook the supplied new high-tension ignition leads to the ignition coils, right to the right hand spark plug and left to the left hand spark plug, coiling them as shown to keep them from resting on the cylinder head.
The next thing we did was static time the engine, which should still be set at 28 degrees BTDC. To do this, turn on the ignition and rotate the Tri-Spark unit fully counter-clockwise, then slowly turn it clockwise until the red light in the unit just comes on. Tighten the pillar bolts.
Here’s our almost finished installation. Simple, compact and reasonably easy to install.
All that’s left now is to button everything up and check running timing with a strobe light. In our case, it was absolutely spot on, requiring no further adjustment. And that’s it, you’re done!