Do You Need To Warm Up Your Engine The Shop Manual
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00:00Here's a question, should you let your bike's engine warm up before you hit the road?
00:05I mean, I wouldn't want to roll out of bed on a cold morning and sprint down the block
00:09without warming up first, and your bike probably doesn't either.
00:13Or does it?
00:14Today on RevZilla we will discuss if, when, and why you should let your engine idle and
00:18warm up.
00:19Let's open up the Shop Manual.
00:31This episode of the Shop Manual is brought to you by Kershaw, my go-to unboxing knife
00:36and a tool I carry with me everywhere.
00:38Get 25% off your order at KershawKnives.com with the code REVZILLA25.
00:45People will cite a lot of reasons for letting their engines idle after startup.
00:49And while there used to be several legitimate justifications for getting the engine good
00:53and warm before clicking it into gear, most of them just don't apply anymore, even when
00:57it's properly cold out.
00:59The first valid, but mostly out-of-date explanation is carburetors.
01:06Up until the 90s, pretty much all bikes relied on carburetors to mix fuel and air in the
01:10right proportions for combustion, and carb bikes just tend to run like crap until they've
01:15warmed up.
01:16They'll idle weird and bog or stall when you open the throttle, and that's because
01:20vaporized gas condenses on still-cool engine parts like the intake tracks, piston crown,
01:25and cylinder walls, leaning out the mixture and causing the engine to stumble.
01:30The solution is to pull the choke, which adds more fuel to compensate for the cold condition,
01:35and then just wait until the engine has enough heat in it to keep the fuel vaporized.
01:39So, if you ride a carbureted bike, then yeah, you gotta give it a minute or two to warm
01:44up or it's just not gonna run right.
01:47With fuel injection, however, the ECU monitors engine temperature and a bunch of other sensors
01:52to ensure a smooth idle and criss-cross response right from startup.
01:56So, as far as proper running is concerned, there is no need to warm up a fuel-injected
02:00bike.
02:02The next formerly legit reason is oil flow.
02:05Perhaps you've heard someone say that you have to allow time for the engine oil to come
02:09up to temperature, because when it's cold, it won't flow properly.
02:13But modern multi-weight oils are multi-weight specifically so they will flow when cold.
02:18In fact, 10W40, that's a common viscosity for street bikes, is designed to pump from
02:23as low as 10 degrees Fahrenheit.
02:25In other words, a lot colder than anyone in their right mind is gonna wanna ride in.
02:29Okay, so if you're on a bike that's 20 years old or younger, then you don't need to let
02:35the engine warm up to clean up the fueling, and you don't need to worry about proper oil
02:39flow.
02:40You do, however, wanna give it a little bit of time for oil pressure to develop and for
02:44oil to get distributed throughout the engine so that things are properly lubricated.
02:48Luckily, that occurs very quickly, and most bikes will even let you know it's happened
02:52by turning off the check engine and oil pressure lights.
02:56So by the time you've pulled on your helmet and your gloves, your bike's good to go.
03:02However, just because you don't need to let your motor warm up before you let the clutch
03:06out does not mean it's okay to send a tack needle to Redline right away.
03:11And that's because whether your bike is carbureted or fuel injected, new or old, American or
03:16Japanese, there is a laundry list of critical tolerances that don't come into spec until
03:21the components have gotten good and hot and expanded to their intended dimensions.
03:26We're talking about the thousands of an inch gap between your pistons and cylinders, as
03:30well as the very precise clearances between your rocker arms, cams, and valves, as well
03:35as lots of other parts.
03:37So if you hammer the throttle before everything has come up to operating temperature, you're
03:41likely causing ever so slightly accelerated wear as the parts flail around at less than
03:46ideal clearances.
03:47Now, that's not to say you can't just hop on your bike and ride, it just means that
03:52you don't want to put the engine under heavy load until it's warm.
03:55If all you're doing is cruising across town to pick up lunch, then just don't worry about
04:00it.
04:01For a full day, healthy engine parts are going to function fine at moderate loads and RPM.
04:06But if you're hopping on a bike to fire down the drag strip or go turn laps at the track,
04:11you're going to want to wait until the clutch cover feels warm to the touch before you bring
04:14the tack needle to redline.
04:17Some bikes, like BMW's S1000XR, even display a lower redline until the engine is sufficiently
04:23warm, just to remind you to limit revs.
04:27To summarize, unless you ride a carbureted bike or have somehow unearthed oil from 1940
04:32and decided to put it in your engine, you don't need to let your bike idle for more
04:37than a minute before you ride it.
04:39So hit the starter, strap on your gear and get on the road, but don't get greedy with
04:43the throttle until the engine has had time to come up to operating temperature.