Installing an Electronic Ignition on a 1973 BMW R75/5

| 10/25/2017 8:30:00 AM

We appreciate that many BMW owners are perfectly satisfied with their stock breaker points ignition system, but we also think that upgrading to electronic ignition is desirable if you ride your old airhead regularly. For one, the stock points on the /5 are hard to adjust. Camshaft actuated, they’re obscured by the mechanical advance unit, making confirmation of proper gap difficult. Further, showing almost 80,000 miles, our subject 1973 R75/5 was developing an odd propensity for points slip, likely from the points lift block wearing. The points were new BMW replacements, but were requiring regular adjustment. And while the mechanical advance unit looked to be OK, with good springs and no indication of undue wear, it appeared to be hanging up, sometimes sticking at full advance.

BikeMasterFollowing our excellent experience with Euro MotoElectricscharging system upgrade for the BMW /5, we decided to check out their EnDuraLast Electronic Ignition upgrade for the /5 and later airhead boxer twins.

This isn’t a difficult project, but it does require patience. The trigger and sensor are easy to install and the sensor wires route out the top of the front cover. To aid routing, we cut a relief in the grommet for the charging wires and ran the sensor wires alongside them, making sure they wouldn’t be pinched when the front cover was installed. A dab of silicone seals it up. 

The control module has three curves. Curve 1 is the default and provides 34 degrees of advance. Curve 2 is for dual-plug heads and provides 28 degrees advance and Curve 3 (which is what we used) is in the middle, providing 32 degrees advance and a slower advance rate than Curve 1. An optional 9-curve module is also available. Installing the module was straightforward and ignition timing was a cinch: With the engine on top dead center, slowly rotate the trigger wheel clockwise until the gap in the wheel passes the sensor and the red light on the sensor board illuminates. Continue to rotate until the light just goes out. After locking the trigger wheel in place, a check with a timing light showed we were absolutely spot on. 

One important note: The otherwise excellent and detailed installation manual says to remove the spark plug caps before adjusting the trigger wheel. This is incorrect, a point verified in a phone call to Euro MotoElectrics. The spark plugs must be connected and grounded, otherwise the module could be damaged when it fires. Never remove a plug lead from a running engine with this system. Also, as the optical sensor is light sensitive the ignition system will likely drop out if the sensor is exposed to direct sun during tuning or, say, a test ride, with the front cover off.

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