A few people in my village, Thais, leave their motorcycles running for a while after they return from a trip. I asked why and was told it lets the motos cool down. My opinion is that the engine would heat up just idling with no air circulating around it.

Anyone else heard of this?

alot of the modern air cooled bike have fan assisted cooling on them so when stopped say in traffic they do not totally rely on forced air

having said that i would think better off shut down i don't know what magic they think they are doing just more fuel burn

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

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.

Thought so, thanks Briggsy.

If you've been fanging a litre bike around the track on the red line for 30 minutes, they do appreciate a circuit at low revs to allow the whole system to cool down a little bit. To be fair, it's mainly the externals of the engine, tranny and exhaust that appreciate less stress and will respond to a cooling down lap. Not to forget the pads and rotors - they will also appreciate a bit of air cooling with no stress to cool them down.

Sure, the airflow and fan assisted cooling are designed to keep the engine internals at the optimum temperature, but park a bike up immediately after a hard run and compare the "ticks" of the metal cooling down compared to a bike that's had a stress free cooling down circuit - big difference.

Honda Wave? Well I guess the same theory applies within reason, but an aircooled bike is not going to get any cooler standing still than it was while in motion with some airflow. It would be smarter to turn off the key and coast for the last 50 metres to get some stress free cooling.

I remember the days when to get the mixture set properly on a 2 stroke performance bike, the optimum procedure was to put brand new plugs into a warm/hot motor, start it and get to maximum speed in every gear as quickly as possible, hit the kill switch and coast to a stop. Remove the plugs and check colour and consistency. If you left the engine running while you slowed down and then turned off, the plug colour was hugely different and gave no real idea of how the engine was running at WOT.

I remember that even though the heads were still hot when you went to remove the plugs (always got burnt until you perfected your removal procedure), they were noticeably less hot than of you'd just stopped normally and switched her off. I eventually learned to remove the tank before the run and just hang a small bottle of juice off the frame. Plug removal was stress and burn free.

It was always fun tuning a 2-smoke, but the local cops where I lived were less than understanding on occasions.

i am not sure the op was talking about( fanging ) what ever that might but i get the idea

of course as soon as you shut down for that leisurely cruise home your indicators and driving lights would cease to function not good in the dark

just a thought

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

Moved to bike forum.

On my Saab turbo you need to have it idle a few minutes if the engine is real hot.

First for the turbo bearings so they get fresh oil pumped inside.

Second if you don't do it the part between turbo and exhaust cracks. And that is no myth, it does crack, maybe not every time but often.

So it could be possible that the same is necessary for high end motorbikes.

My CB500X will run the cooling fan with the engine off (but the switch on) for a bit after the bike has been running; especially after a trip through BKK. So perhaps there's a bit of folk wisdom in doing it, but most likely only after heavy loads at low speeds when the engine isn't as cooled off my the air rushing by.

...

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.

I think it might hurt - it might warp the metal if it was hot enough.

My PCX has an idler which cuts the engine of when you stop, if it is set that way, so it cannot be doing any harm. Suppose you are riding for miles, then you come to a red light.

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

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.

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.

Idling a bike to "let it cool slowly" makes no sense. Regardless of whether a bike is air cooled or water cooled, the engine and exhaust will get hotter, if left idling. I say this based on personal experience with both air cooled and water cooled bikes.

You idle a bike at start to warm it up....and you idle it at stop, to cool it down?

As for the whole "lessen engine stress due to differential cooling" theory, that also makes no sense. Cooling is basically the rate at which energy flows from the engine or radiator internals to the ambient environment (the air). An engine in motion will have a greater energy gradient (rate of cooling) than an engine at rest due to the big differences in air flow over the engine (and radiator/cooler). A stopped engine will cool slower...and with a lower gradient, differential temperatures within the engine will be less. Hence, less stress.

Just to be clear: my advice is turn off your motorcycle when you are done with your ride. An idling engine just generates more heat, consumes gas, pollutes more, and adds to the noise.

Idling a bike to "let it cool slowly" makes no sense. Regardless of whether a bike is air cooled or water cooled, the engine and exhaust will get hotter, if left idling. I say this based on personal experience with both air cooled and water cooled bikes.

You idle a bike at start to warm it up....and you idle it at stop, to cool it down?

As for the whole "lessen engine stress due to differential cooling" theory, that also makes no sense. Cooling is basically the rate at which energy flows from the engine or radiator internals to the ambient environment (the air). An engine in motion will have a greater energy gradient (rate of cooling) than an engine at rest due to the big differences in air flow over the engine (and radiator/cooler). A stopped engine will cool slower...and with a lower gradient, differential temperatures within the engine will be less. Hence, less stress.

Just to be clear: my advice is turn off your motorcycle when you are done with your ride. An idling engine just generates more heat, consumes gas, pollutes more, and adds to the noise.

You idle a bike at start because it is not at operating temperature. If it is above that temperature when you stop than allowing it to idle will bring it down to that temperature; no further. If you ride like a grandmother and have plenty of airflow it's a good chance that idling it when stopping will indeed raise the temperature.

As I alluded to earlier, I split the difference. I stop my bike and then kick the key back on. If the radiator fan runs, I leave the key on until it cuts out. Then the bike is turned all the way off.

You idle a bike at start to warm it up....and you idle it at stop, to cool it down?

Actually, I idle my bike at start-up for two reasons.

1) to get to operating temp before riding.

2) with the aftermarket exhaust system it is a second alarm clock for my other half to come downstairs and chop-up and prepare my fruit breakfast so I can take it to work.

works a treat for both.

Perhaps if I do it on returning, as well as dissipating the heat more evenly, it will send her into the kitchen to get dinner ready.

" If it is above that temperature when you stop than allowing it to idle will bring it down to that temperature; no further. "

Unless your bike is overheating, when you stop, it is within the normal range. I have a temp gauge on my water cooled 650. My bike runs a bit hotter idling than it does at cruising speed (80-120 kph). I am guessing that is even more true for an air cooled bike.

If you are really pushing the bike, then my advice probably does not apply. Yeah, the engine is going to get hotter than normal, once around the track for a cool down is a good idea.

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

Honda Click has a fan. It is water cooled.

Honda Wave is air cooled. All they are doing is over heating it.

I watch Thais walk away from Harley's leaving them running. It baffles me.

I dont understand why you would leave the fan running with the engine off.. there is no circulation of coolant. your just cooling the radiator

I dont understand why you would leave the fan running with the engine off.. there is no circulation of coolant. your just cooling the radiator

Assuming you're addressing me, my 500X has the fan on the rear (as most bikes do) of the radiator. Thus it sucks air through the radiator and blows over the cylinders.

When riding quads offroad, we often get the rads plugged up with mud and the machine would start overheating. The quickest way to cool it off is to shut the engine and let the blower fan run until it shuts off, then start it up again for 10 sec of so and let the fan run again, do that 3-4 times and it's good to go. This way you let the coolant circulate. Just shutting it off won't definitely help in any ways.

I dont understand why you would leave the fan running with the engine off.. there is no circulation of coolant. your just cooling the radiator

Assuming you're addressing me, my 500X has the fan on the rear (as most bikes do) of the radiator. Thus it sucks air through the radiator and blows over the cylinders.

Not sure if that will help much... Won't hurt anything either.

I dont understand why you would leave the fan running with the engine off.. there is no circulation of coolant. your just cooling the radiator

Assuming you're addressing me, my 500X has the fan on the rear (as most bikes do) of the radiator. Thus it sucks air through the radiator and blows over the cylinders.

Not sure if that will help much... Won't hurt anything either.

Maybe not. But my rationale is that since the electrical thermostat is in the cylinder head, and Honda programmed the fan to run at greater than X* C, letting the fan run until temperature drops below that won't hurt anything....

I dont understand why you would leave the fan running with the engine off.. there is no circulation of coolant. your just cooling the radiator

Assuming you're addressing me, my 500X has the fan on the rear (as most bikes do) of the radiator. Thus it sucks air through the radiator and blows over the cylinders.

Not sure if that will help much... Won't hurt anything either.

Maybe not. But my rationale is that since the electrical thermostat is in the cylinder head, and Honda programmed the fan to run at greater than X* C, letting the fan run until temperature drops below that won't hurt anything....

But the cooling system is to prevent the engine from overheating, something which it wont do if its switched off.. though for turbo its another story.

but for me personally, If i was thrashing an engine I probably wouldn't turn it off in an instant but for normal use its just contributing to wear and tear.

But the cooling system is to prevent the engine from overheating, something which it wont do if its switched off.. though for turbo its another story.

but for me personally, If i was thrashing an engine I probably wouldn't turn it off in an instant but for normal use its just contributing to wear and tear.

It's my understanding that for a turbo'd engine it's not for the engine, but to cool the turbo down to a point that the oil won't 'coke' up in it.

But the cooling system is to prevent the engine from overheating, something which it wont do if its switched off.. though for turbo its another story.

but for me personally, If i was thrashing an engine I probably wouldn't turn it off in an instant but for normal use its just contributing to wear and tear.

It's my understanding that for a turbo'd engine it's not for the engine, but to cool the turbo down to a point that the oil won't 'coke' up in it.

Yes thats correct, I think its something to do with high heat and bearings in the turbo with lack of oil cooling..But the whole system is a lot hotter that an engine

Just like your heart ,you only have so many heartbeats.I believe it's the same with an engine piston revolutions,there

Are just so many.So with that in mind,maybe you should run more,maybe die sooner.For as the motorcycle maybe

Leave it running as much as possible maybe it won't last as long

Being I was A tractor trailer driver in hot weather.I would start it at the beginning of my shift on A Sunday afternoon.

I would not turn it off for any reason,fueling,dinner break,at night when sleeping etc.When I would finish my shift

Saturday morning I would turn it off.