Fuel Injectors Vs. Carburetors
For decades, Harley Davidsons needed to be warmed up which is why this activity is still the default setting for many old schoolers. Carbureted engines needed a precise air/gasoline mixture, and when cold-started and the throttle opened up, it would stall. The vaporized gas would condense on the cold steel pistons and cylinder walls. The choke would have to be engaged restricting the air and compensating for the cold conditions leaning out the air for a more fuel-rich mixture until the machine was warmed up.
Since 1995, Harleys now have fuel injection. With fuel injectors, the ECU (electronic control unit) calculates the precise amount of fuel and directs it into the cylinder gauging the amount needed in any condition, cold or hot. Now, when starting your Harley even in cold weather, it’s not necessary to wait several minutes for the air/fuel mixture to harmonize.
Modern Oil Viscosity Has Changed
Pre-World War 2, motor oil was straight-weight minerals and like sludge when it was cold. Today with multi-grade oils, your Harley’s oil is made for any condition. Even the common 10W-40 is good to go at 14 degrees which is well below freezing and much colder than most bikers will ever go out in. Your oil does not need warming up. However, it does need to be pumped throughout the engine to lubricate all the parts, and this happens very quickly. Normally, your bike tells you exactly when the oil is distributed by turning off the check engine light which is connected to the oil pressure sensor in the sump. Within thirty to forty-five seconds, your fuel injectors have directed gas in the exact amount for a smooth start and idle, and the oil in your engine has been distributed properly. With your modern engine able to engage and rev up within less than a minute, is there any reason to not take off and gear up down the road?
Different Metals Warmup at Different Times
While your Harley is ready to take off in under a minute, you still shouldn’t ride hard right away. Warming up the engine by riding smoothly is still important. Revving your engine to the red line too soon while it’s still cold could damage your engine by scuffing the pistons. Metals in your motor do not warm up simultaneously. Harley’s pistons, heads, and rocker boxes are made of aluminum, but the studs holding them in place are steel which warms up at different rates.
Harley has made the cylinders with enough space for heat expansion with extra ring end-gaps to prevent binding. In a cold engine, the clearances are meant to compensate and even over-compensate for these warmup times including a two-thousandths of an inch to the cylinder walls vs a half-thousandths when hot. Still, it’s not smart to throttle up a cold engine quickly. The average warm-up time when riding smoothly is about ten miles at 65 MPH.
So the standard operating procedure should not be turning the key and leaving it idle for five or six minutes. No oil has to be warmed up, and no air/fuel mixture needs to be refined. Just start up your Harley, adjust the mirrors, put your helmet on, and zip up your jacket. That’s all the time you need. Your check engine light will turn off indicating the oil pressure is primed and all engine parts are lubricated.
Of course, you still don’t want to peel out and redline your engine cold. But taking it easy for the first few miles will keep the expansion rate of metal swelling consistent so that your Harley runs smoothly and within the specifications to keep your engine running without incident for years to come.