Do Harleys Need To Warm Up?

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You’re about to jump on your Harley-Davidson motorcycle and take off, but what about warming it up? Is it necessary to wait for the engine to get warm?

For some reason, this has been the topic of discussion and confusion for bikers everywhere. Science has been left outside in the cold for this debate too many times because technological advances have changed the answer. It’s about time we allowed logic to inform our pre-ride traditions after turning the key on our Harley.

Harley-Davidsons, like every motorcycle, need warming up before redlining the throttle down the freeway. But how much time is required? Having scientific answers to this question will save both time and money.

You’ve heard your neighbor warming up his Harley for over five minutes early on a Saturday morning and have wondered why. Is it really necessary to wake up the whole block to get the engine up to temperature? He may believe that in order for the oil to thin out and flow properly, the engine must be at a certain temperature. He also may think the pistons will be scored if he takes off on a cold engine. The answer to that question (like almost every question in life) is it depends. It depends on whether it’s a pre-fuel injected, carbureted bike. Other than that, the answer is no. He’s wasting his time and your sleep.

I’ve taken a historical trip up the evolutionary ladder of the Harley-Davidson to understand why people warm up their bikes as long as they do. I’ve checked with experts and scientific websites explaining the technical data of engine function and oil viscosity to understand this age-old debate and share my findings with you. Once you see the facts, I think you’ll agree that most people warm up their Harleys for way too long.

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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.

About THE AUTHOR

Benjamin Rathbun

Benjamin Rathbun

Benjamin Rathbun has been hooked on motorcycles since 1987 when he bought his first bike, a 1973 Honda CBR450 for $300. Since then he has been through countless bikes and continued his two-wheeled hobby passing it down to his 21-year-old son who rides with him on the weekends in the Blue Ridge Mountains. Benjamin believes that nothing clears the mind faster than flying 26 inches above the asphalt on his Harley-Davison.

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