This article was written with Moto Guzzi loopframe motorcycles –V700, Ambassador, and Eldorado– in mind. These have an external distributor with cap. The underlying principles invoked are similar for other engines. The retired mechanic (Thank you, Ed Bickerstaff!) who taught me this many years ago called it “power timing”. I have used this method with cars, trucks, and motorcycles with point ignitions for almost 30 years. It is very simple for a mechanically-inclined person to implement, but it also has the potential to damage or destroy an engine if performed improperly or without understanding the underlying principles.

Setting ignition timing without a timing light is considered by some to be inexact and dicey. The converse thought –harbored by the less-trusting– is that using a timing light requires all of the markings to be indexed precisely to be valid. On older engines, part and assembly tolerances were sometimes looser than they are now.

Loopframes are very well engineered, but the engineers didn’t build them, hourly assembly employees did, and in the gap between engineering and manufacturing lurk the marketers and bean-counters. So the timing marks are probably in a safe-for-1960’s-manufacturing-tolerances, but not necessarily optimal, position. And that placement was for fuel formulations from the 1970’s when leaded fuel was still available and ethanol was called Dry Gas and was used to remove water from fuel instead of what it does today.

The goal of setting timing is to provide maximum possible responsiveness while protecting the engine from damage. If the reference marks are improperly placed, different fuel is used compared to what was used to set the timing, and/or the atmospheric conditions change due to altitude and the rider does not recognise the sound of pinging or understand its consequences, the timing light method may actually contribute to the premature destruction of the engine. The marks are probably purposely conservative to prevent such possibilities. This leaves a little room for improvement if implemented with responsibility and vigilance.

Pinging is a high-pitched and subtle sound, often described as sounding like aluminum foil being crumpled. It can sound like a jingling keyring as well; I use only a single key in the ignition to prevent confusion. Pinging will be heard when accelerating in a gear that is too high or when when lugging up a grade or against a strong headwind or with low octane fuel or overly lean mixture or some or all of those combined. Shifting down can quieten the noise, but the engine still may still be pre-igniting more subtly, which causes the internal combustion to react against the direction of the piston rather than with it.

If the spark comes at the correct time the flame front and resulting expansion will occur to push the piston when it’s on its way downward. If it is too early, the piston movement will be forced against that expansion and catastrophic metal failure of internal parts will commence.

A timing light can’t detect pinging. Timing lights aren’t connected to the engine while it is in actual use conditions, they are typically used in static situations with no load or rider error. They are used with whatever fuel happens to be in the tank, so timing could be set with 93 octane and the subsequent tank could be marginal 86 from a rural station, resulting in miles being run with too much advance and pre-igniton more likely on every uphill and headwind.

Ideally the best way to set timing would be to do it under actual riding conditions, with the ability to adapt to differing conditions such as fuel quality, altitude, and load. This is what modern electronic management systems with ping and knock detectors do. And what these instructions set out to do for people with point ignitions who want optimum performance are are willing to pay attention. This requires the rider to get involved and pay heed to the mechanical noises and behaviors. The idea is to empower the rider of a loopframe or other vintage bike to keep their engine from pinging regardless of conditions faced, while not compromising performance more than needed.

Please Stop and Consider: If you aren’t willing or competent to pursue this thoroughly, you could damage your engine by leaving it set where it pre-ignites (pings) itself to death. If you read through this and feel that it is “over your head”, it is strongly suggested that you find a trustworthy mechanic and have them set your bike for the worst case you expect to encounter. Fill the tank and run the bike for a while with the lowest octane you might encounter before taking it to the shop. In some rural areas only “regular”, 85 or 86 octane is available.

That said, if you are self-responsible

We start by assuming that the carbs are adjusted properly. There will be give and take, you might find that want to redo jetting* after you do this.

Set point gap carefully, keeping in mind that the width of the gap can affect the timing. I set mine to the minimum specified gap, for loopframes that is 0.42 mm, or 0.016 inches which is a bit smaller. This advances the ignition the least and gives a longer dwell time. Also have good plugs/wires/cap/rotor/advance springs and recent fuel. Points like to close themselves, so a recheck of the gap after adjusting them and riding for a while is good practice.

If you want a way back to where your timing was set, mark the original timing setting with a sharpie by putting a line on the distributor and base so that you can return to the original setting easily. On loopframes counter-clockwise advances the timing. On most engines, advance is generally the opposite of the direction the rotor or hub turns when the engine is running, retard is the same direction.

distadvance

Start the engine. When it’s warmed up, loosen the distributor hold down bolt and turn the distributor to where the idle sounds best, typically fastest, but also feel how it vibrates. Note which way you turned it from where it was already set and how much. Then retard a bit, say 1/8 to 1/4 inch clockwise. When you find your initial setting point, tighten the distributor bolt.

If the engine won’t run at all and wasn’t set before, start in the middle and work outward from there until it runs, then do the above. It is possible that the distributor might be installed incorrectly and may need to be pulled out and rotated a tooth versus where it was on the drive gear. If it ends up running way at one end of the adjustment, it might be better to realign the distributor so that the basis point is in the center of the adjustment travel.

Time to go for a ride on a quiet road where you can pull off easily and safely, taking an appropriate wrench with you to loosen the distributor hold-down bolt. I use a 1/4″ socket wrench with extension and 10mm socket. When it’s been running on the road for a bit and settled in, lug the engine lightly; hit a hill or a headwind in too tall a gear or at too low an RPM and apply throttle. Don’t be abusive, just simulate being tired and momentarily forgetting to downshift into that resistance. Do it briefly! But long enough to listen for pinging.

Did you hear pinging (crinkling aluminum foil sound, sometimes it sounds like a keyring jingling) when you applied throttle under load? If so, pull over and retard a bit more (turn distributor CW). Repeat as necessary. Pinging can be very hard to detect over intake and exhaust roar. As you get closer to the right setting it will be fainter and harder to hear, so maybe do one more retard if you are new to hearing pinging or are unsure. Wearing earplugs can actually help with detection by reducing other mechanical noises.

What you will end up with is the maximum advance possible with the fuel you have in the tank at the time in the barometric conditions at the time with your current carb settings. If it gets hotter, if you have to buy lower-grade fuel, if you install leaner jets, you might need to retard further. You may end up back at your sharpie mark after all this exercise. If so, good, your timing marks are useful. If not, then keep your ears open for pinging while you ride and keep that wrench handy. Points can readjust themselves as time goes by, and change the timing when they do.

*These ideas derived from posts by Greg Field on various Moto Guzzi forums and lists, interpretations are mine.

-If you have a choke on the bars, try opening it a bit when you get pinging, to see if it lessens. If it does, richening fuel mixture with larger jets can also help, but possibly at a cost of mileage and driveability. Balance is the key, a bit of retardation and a small jetting increase or needle raised a notch might be better than doing all of one or the other.

-Also, squish clearance was notoriously loose on many engines during that time, and tightening squish can reduce pinging while improving compression and power. A typical way to reduce squish is to build with thinner or no base gaskets, and then carefully check all clearances. A search for how to check clearances with pieces of solder should find useful articles. Ducati and Moto Guzzi motorcycles from the 70’s often benefit from tightened squish.