Leaving motorcycle idling after a journey, good or bad?

[rakman]

Running any ICE at high load generates more heat. Slowing down and using light throttle for a few minutes while moving will allow the head and cyl temp to drop, which will help keep the oil from breaking down in the heat soak.

But running the engine and not moving (unless water cooled with a fan) will make the engine hotter.

Running a turbo charged engine at idle for 30 seconds allows the turbo internals to slow down. When the engine stops, the oil flow stops (unless you have an accumulator) and the turbo bearing could get damaged if left spinning at high speed. As well as preventing "coking" of the the oil from the heat.

Diesel engines actually run cooler at idle, where gas engines get a little hotter at idle. Since Diesel engines have no throttle plate, the get their running speed by the amount of fuel injected. At idle it's a minimum amount of fuel. A gas engine actually needs a little more fuel at idle than running at the BSFC (Brake Specific Fuel Consumption) speed.

Edited February 26, 2015 by rakman

[Kerryd]

It's probably just "old school" thinking passed down from parents/grandparents. I got it from my dad. After we did a long trip somewhere, he'd always let the truck idle for a few minutes while we unloaded (whatever). Back in the day it was thought that if you shut a hot engine off without giving it a chance to cool down, it could crack the block (or cause other parts to warp). Same thing for chainsaws and even ski-doos !

It drove us bonkers in the military when we received this new style of jeep that had a fan that would keep running after the engine was shut off. Our first impressions were that there was an electrical problem or something. The grease-monkeys told us it was designed that way because the manufacturers used thinner engine blocks, the fan needed to keep running until the engine cooled down enough that the block wouldn't crack. Yeah, real tactical when you kill the engine and are listening for enemy activity and suddenly your engine fan kicks in. Might as well stand up and shout "I'm over here" !

Still, not as bad as the "ceramic" brake pads they put on a different "tactical" vehicle. Brand new brake pads that would shriek like a Banshee in pain at the lightest touch of the brake pedal. How those made it through the acceptance testing we'll never know.

Other "old school" things I see here now and then include the "crank the throttle twice and hold it open a bit then hit the starter button" method of starting motorcycles, even brand new ones with Fuel Injection (that normally start just fine as soon as your touch the starter button). Holdover from the days when you needed to get a bit of fuel into the carb before kicking it over (used to have to do that as well on some cars I owned back in the 70s/80s).

And the whole "driving without headlights" thing. I asked about it before and the perception is that they use less fuel by not turning on the headlight ! Funny thing is, no one seems to be able to come up with a figure for how much they are (supposedly) saving, they're just going by what someone else told them. Of course all of them are such awesome riders that there's no chance they'd ever get into an accident by riding their bikes at night without headlights on poorly (or unlit) roads full of other motos, people, dogs, obstructions, etc. The Darwin Awards may have to add a special category just for those guys.

(I saw the whole "no headlights at night" thing in India too and the people I talked to said pretty much the same thing - they use less fuel by not using their headlights !)

[northernphil]

A few points here. Throwing water over the brakes on a bus ! Time to take a different bus . Reving the engine and switching off. This was done on pre war racing Bentleys , the idea being that the magneto was off ( earthed ) the revs sucked in fuel so there was fuel in for the man brave enough to hand crank it. I even remember reading that the magneto lever on the steering whel could be moved and their was a chance that the engine would fire as a good chance the engine last stopped with a piston being at the top of the stroke. I had a Citroen Xantia turbo deisal about 20 years ago and I was told to let the engine idle for 10 secs before switching of or else the turbo could overheat due to oil not getting pumped round.

But Honda Waves , stop go ,stop go, switch them off , enough bad air here when they are moving.

[ToddinChonburi]

I love the crap Thai's do , because someone said. I say, why do you do that ? because someone said is was a good idea.

My Thai GF ask me a ? and now I laugh and say, what did DR. Google say ?

Face Book has all the answers.

Back in America I watched a guy drive circles around the parking lot, when asked what he was doing he stated , Cooling his Tires ,

[jdinasia]

My friend (5 minutes after returning home) thinks turning off your bike is the way to go.

[northernphil]

ImageUploadedByThaivisa Connect1424921724.321845.jpg

My friend (5 minutes after returning home) thinks turning off your bike is the way to go.

He looks exhausted .

[ChiangmaiRob]

Thanks Gerry, the bikes in question are just standard Honda Waves. No fans.

Just shut it down Coota, the wave and all other scooters you see in Thailand don't need to idle before shutdown. There are cases where you should "cool/slow" down some engines, and I won't go into detail, but for just normal every day riding your wave, just stop and shut it down.

BTW, I am a mechanic to trade so I do know what I'm talking about.

[ChiangmaiRob]

Running any ICE at high load generates more heat. Slowing down and using light throttle for a few minutes while moving will allow the head and cyl temp to drop, which will help keep the oil from breaking down in the heat soak.

But running the engine and not moving (unless water cooled with a fan) will make the engine hotter.

Running a turbo charged engine at idle for 30 seconds allows the turbo internals to slow down. When the engine stops, the oil flow stops (unless you have an accumulator) and the turbo bearing could get damaged if left spinning at high speed. As well as preventing "coking" of the the oil from the heat.

Diesel engines actually run cooler at idle, where gas engines get a little hotter at idle. Since Diesel engines have no throttle plate, the get their running speed by the amount of fuel injected. At idle it's a minimum amount of fuel. A gas engine actually needs a little more fuel at idle than running at the BSFC (Brake Specific Fuel Consumption) speed.

Diesel engines do have a throttle plate to regulate the air, and the fuel injected is proportional to the amount of air being inducted, whether this is a direct mechanical link between the throttle plate linkage on the inlet manifold and the fuel pump (old style) or if it's done electronically, the fuel and air mix are linked. But it is the volume of air that dictates the volume of fuel which together dictate the engine speed.

[FredNL]

FOR TURBO ONLY !!!

If you have a TURBO engine it would be wise to have the engine idling for about 1 minute before you turn it off.

Reason: The (exhaust) scoops in the turbo are (red) hot. The axle where the scoops are on is cooled with oil. The function of the oil is not only lubricating but also cooling.

When you turn the engine off with with red hot scoops in turbo, the axle won't receive (cold) fresh oil for cooling. The oil will "burn" and will leave burned sludge on the axle and bearings. Also there will be a hot side (exhaust) and a cold side (inlet) without cooling the axle, it may get some problems, like bending... Nowadays the materials are way better but prevending turbo damage I would advice keep the turbo engine idling for about a minute.

All other cars or motorcycles without turbo, it would be better to turn it off as soon as possible.

Reason: Pollution of cylinder(s), sparkplug, valves (best combustion is at maximum torque rpm), pollution of the environment.

[FredNL]

This is not a joke !!!

This is why many Thai don't use (head)lights on their vehicles.

It was my girlfriend about 4 years ago that asked me how high my (home) electric bill was. I asked her why she wanted to know.

She told me that she would not use any lights when driving when possible, as many Thai do. I asked her why. She said it was because I was driving in my car with my (head)lights on during the day when doing distances. People would think that I was crazy.

I still think that driving with headlights on during the day is safer in Thailand than without.

I asked her what the connection with my electricity bill was.

Her answer: "The electric company (at home) would charge me more when driving my car and using headlights during the day !!!"

And she had a masters degree from Mahidol University ! (She probably <deleted> her way passed the exams)

Edited February 26, 2015 by CharlieH

[papa al]

Radical idea:

Follow manufacturers recommendations as per users' manual.

If it doesn't say to let it run, then I guess it is not important.

Since 1967, no probs.

On the other hand, I had a little Chevy that ran very quietly and I accidentally left it idling for 9 hours.

Again, no prob.

Harleys can idle without revving the shit out of them?

Who knew?

Edited February 26, 2015 by papa al

[ChiangmaiRob]

FOR TURBO ONLY !!!

If you have a TURBO engine it would be wise to have the engine idling for about 1 minute before you turn it off.

Reason: The (exhaust) scoops in the turbo are (red) hot. The axle where the scoops are on is cooled with oil. The function of the oil is not only lubricating but also cooling.

When you turn the engine off with with red hot scoops in turbo, the axle won't receive (cold) fresh oil for cooling. The oil will "burn" and will leave burned sludge on the axle and bearings. Also there will be a hot side (exhaust) and a cold side (inlet) without cooling the axle, it may get some problems, like bending... Nowadays the materials are way better but prevending turbo damage I would advice keep the turbo engine idling for about a minute.

All other cars or motorcycles without turbo, it would be better to turn it off as soon as possible.

Reason: Pollution of cylinder(s), sparkplug, valves (best combustion is at maximum torque rpm), pollution of the environment.

Under normal running, the exhaust manifold and the turbo are never red hot, and I'm talking about a 100 - 120km/hr down the highway. It's only if the engine is hammered at a sustained 80-100% maximum revs, your exhaust system will glow red hot, and I'm only talking about a petrol engine, not a diesel. If you don't believe me then try it, in the dark is best as you will see any red glow easier. I'm not saying it's not possible, but I've never seen a diesel engine exhaust glowing red hot, and I've had a few diesel motors.

[papa al]

Running any ICE at high load generates more heat. Slowing down and using light throttle for a few minutes while moving will allow the head and cyl temp to drop, which will help keep the oil from breaking down in the heat soak.

But running the engine and not moving (unless water cooled with a fan) will make the engine hotter.

Running a turbo charged engine at idle for 30 seconds allows the turbo internals to slow down. When the engine stops, the oil flow stops (unless you have an accumulator) and the turbo bearing could get damaged if left spinning at high speed. As well as preventing "coking" of the the oil from the heat.

Diesel engines actually run cooler at idle, where gas engines get a little hotter at idle. Since Diesel engines have no throttle plate, the get their running speed by the amount of fuel injected. At idle it's a minimum amount of fuel. A gas engine actually needs a little more fuel at idle than running at the BSFC (Brake Specific Fuel Consumption) speed.

Any engine will have different BSFC values at different speeds and loads, right?

[KhnomKhnom]

Unless there is a fan, there is no benefit to keep a motorbike running.

This same is true for a car or pickup but some have fans connected to a timer and the fan continues running for a while after the engine is shut down. I suspect the fan is on a real timer and not thermostatically controlled to run based on the heat. In either case, just turning the car off to cope with heat is the best practice and if it has an automatic fan function, it will take care of itself. Emergency over-heat is different.

I encountered a taxi driver in Moscow who turned off his headlights between each stop sign and the next one. He explained that was to save the headlamps because headlamps were difficult to get. I asked him if he could easily get on-off headlamp switches. No answer.

I held back from noting that frequent turning on of incandescent lamps shortens their functional life.

Otherwise, leaving a motor running when it is likely to charge up its battery does make sense, but only at a motor speed where the alternator provides more charging than the battery is discharging to keep the motor running. Alternators, rather than generators, are supposed to generate enuf even at low speeds.

Old carburetor car users sometime felt that a sharp acceleration of the motor just prior to shut off would flood the system with fuel that would be there ready to assist the next start up. That did not account for evaporation of the fuel nor the possible flooding if lots of liquid fuel is present next start-up.

[mercman24]

absolute load of rubbish, racing motorbike engines are not run at low revs to cool them down, when they stop - they stop, ok, and as to the post about SAAB turbos what was that about , the saab turbo was sh*te as they were common for blowing turbos as it was a design fault the turbo didnt get enough oil resultng in bearing failure, cant see what it had to do with motorbikes though,

[Anon999]

It is not just motorbikes, the myth persists with pick-up trucks too.

The confusion may arise as there are active cooling systems in operation such as pumps and fans operating when the engine is running (and sometimes when the engine is off but the key is in the ignition). However the overall entropic (Is that the right term?) situation would be better served by simply turning the engine off.

In days gone by, there were other theories about revving the engine or idling the engine before turning it off but I am confident it is not a necessity.

On a connected point, take a bus or taxi in Burma and at every garage and stop the driver will cool the brakes by sloshing water over them. Can't hurt but again a hangover from yesteryear.

Some of you may remember that a long time ago when you engaged the handbrake on a hill that once they cooled down it required a lot of effort to release it as the drums had contracted onto the brake shoes. If you tried throwing cold water over disc brakes then there was a good chance the discs would crack!

[sate ayam]

After racing (ahum) up to the summit of doi inthanon on the 125 wave (minutes of first gear high revving) I parked it with it's head facing the slightest breeze and let it idle for a good 3 minutes.

Why? something in me said the engine oil might be a little hotter than my usual commute

80k and counting, engine never opened

[BradinAsia]

any engine driven hard should be run at idol for awhile to let the heat even out.

I beg to differ...

Having ridden bikes all my life and having worked 10 yrs in service/maintenance in the (Honda) motorcycle business

I'd say there is absolutely no benefit to letting the bike sit and run at idol after a trip or after a race.

The professional auto and motorcycle racing teams never do that.

Edited February 28, 2015 by BradinAsia

[williet98248]

The same ones who dont switch light on to save battery...

Nonsense.

That's done as to not attract ghosts.

Strange things engines, I have never done it, but perhaps will start to after arriving home from a day's tour at almost WOT. My common sense would have said that turning the engine off would cool it down better than letting it run at idle for 5 minutes, then turning it off. But hey, there ya go.

Than the external sections would cool faster than the internal ones. Leaving it running for a bit keeps coolant flowing through the system and moves some more heat outwards.

There is no coolant system in an air cooled engine. Whether air cooled or liquid cooled; just turn it off.