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General Category >> Rubber Side Down! >> Engine staying hot for several hours after riding?
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Message started by 07S40rider on 07/19/08 at 04:59:10

Title: Engine staying hot for several hours after riding?
Post by 07S40rider on 07/19/08 at 04:59:10

Should I be concerned? I ride my S40 to/from work, about 11 miles each way. I usually get home around 5:30 and I have noticed that the transmission casing on my bike is still too hot to touch as long as 2 hour later. It seems to take a full 4-5 hours before the noticeable warmth goes away. Is it normal for it to take so long for an engine to cool down after a 20 minute ride? Engine oil level is good - about halfway between the Low and Full marks. The exhaust seems to cool down very quickly and does not stay hot like the transmission part of the engine. The bike seems to be running fine otherwise, although I am still in the break-in period (340 miles as of yesterday). Any input would be greatly appreciated.

Title: Re: Engine staying hot for several hours after rid
Post by Oldfeller on 07/19/08 at 05:11:28

Lots of pounds of steel and aluminum there -- go feel your car's block after two hours and see what it feels like.

Title: Re: Engine staying hot for several hours after rid
Post by SuziQ on 07/19/08 at 05:31:44

When I return from a ride on any of my bikes I always leave them to cool somewhat outside in the drive in the shade where the air can circulate. I have a neighbour who rides into the driveway, opens the garage door, puts the bike in a hot garage, closes the door and leaves it to bake.

Title: Re: Engine staying hot for several hours after rid
Post by 07S40rider on 07/19/08 at 05:33:34

6D4B44576F3E0 wrote:

Dang, so YOU are the weirdo living next door to me eh!?! :o

Title: Re: Engine staying hot for several hours after rid
Post by buttgoat1 on 07/19/08 at 06:00:16

sounds normal. I used an infrared thermometr before on an old Gravely lawn tractor. I could not believe some of the temps I was getting. The exhaust manifold was in the 900 degree range!
My point is that the engine gets up to operating temp and can stay there indefinitely so it shouldnt be a problem even in a garage.

Title: Re: Engine staying hot for several hours after rid
Post by Charon on 07/19/08 at 06:40:54

I often, but not always, leave my motorcycles out in the breeze to cool for a while before putting them in the garage. I doubt it makes any difference to the life of the motorcycle, but it helps keep the garage a little cooler.

Quite a few years ago I was mowing some heavy grass with a riding mower that had an 8-horse Briggs engine. It was late in the evening, really getting too dark to mow. I chanced to look down at the muffler and saw it was glowing orange. There was blue fire extending a couple inches out of the end of the pipe. That engine was probably working a LOT harder than the engine on any motorcycle, but that was the first time I had seen an exhaust system glowing from heat. I have read stories in which people flying the old radial aircraft engines referred to the red glow of the exhaust collector rings, but I have never seen that.

As a very rough rule, an internal combustion engine converts about a third of the heat it produces from burning fuel into mechanical work. Another third is wasted into the cooling system, and the last third is wasted as hot gas out the exhaust pipe.

Title: Re: Engine staying hot for several hours after rid
Post by 07S40rider on 07/19/08 at 07:15:28

Thanks everybody. You have convinced me that it is perfectly normal. In fact I am so convinced that I just took a nice Saturday morning back country road ride. :D

Title: Re: Engine staying hot for several hours after rid
Post by SuziQ on 07/20/08 at 06:16:52

46514257515651425D300 wrote:

The engine temperature will increase when shut off and movement of the bike and airflow ceases, so the temperatures increases for a period of time which isn't of a great concern for the engine. But there are electronics on the chassis around and on top of the engine, not many on the S40's but it is still nice to think of them. The greatest enemy to the electronics is heat, vibration and dust and dampness probably in that order. When the airflow stops their optomistic operating temperature also increases and just like the rider like to sit in the shade in a cool breeze for awhile.

Title: Re: Engine staying hot for several hours after rid
Post by justin_o_guy2 on 07/20/08 at 18:46:35

I've heard this, but I cant figure from whence does the heat come that increases the engine temp after shut off. Seems to me that if I extinguish the fire that is creating said heat, it should only get cooler.Anyone help me unnerstand this, or is it urban legend>?

Title: Re: Engine staying hot for several hours after rid
Post by serowbot on 07/20/08 at 18:57:02

The core temp will not increase once you shut down.
But the heat at the core will now radiate out to the formerly air cooled outer part of the engine. So from the outside, you will feel more heat coming off the engine. Also as the oil drains away from the hot parts, they can no longer transfer heat away from themselves and piston rings can then seize to the cylinder wall. Ouch!

Title: Re: Engine staying hot for several hours after rid
Post by Charon on 07/20/08 at 19:04:57

The phenomenon is known as "heat soak." The engine generates heat internally as it runs. That heat moves from the combustion chamber (including the piston crown) through the metal to the coolant, whether that coolant be liquid or air. When the engine shuts down the coolant flow usually stops. Residual heat continues to flow out of the engine, but the coolant is no longer removing it. The result is that the engine usually heats up a little, then begins to cool by normal air circulation around it. On liquid cooled engines the coolant can still circulate by convection. On those liquid-cooled engines with automatic electric fans you can often hear the fan start and run for a few moments right after engine shutdown. You don't see the temperature change on the gauge (if any) because the gauge's power is removed when the ignition is shut off.

In the case of a non-fan-forced air cooled engine - most air cooled motorcycles - the last couple of moments of idle as you ease into the parking space or garage generate heat from the running engine, but no airflow for cooling. Same thing happens idling in traffic. That heat contributes to heat soak.

A classic example of heat soak was the R4360 "corncob" radial engine used in the B-36 bomber. It was buried inside the wing of the airplane, and was fan-cooled. It frequently happened than an engine which had been running perfectly at landing would have problems on start-up because of the heat soak.

Title: Re: Engine staying hot for several hours after rid
Post by justin_o_guy2 on 07/20/08 at 19:39:28

Thanks folks, now I get it.

Title: Re: Engine staying hot for several hours after rid
Post by T Mack 1 on 07/21/08 at 17:11:01

Another comment here.

I noticed while trying to tune the carb, If I leaned out the setup, the bike ran hotter. Which, of coure took longer to cool down. Got a little better MPG. But ..... being I bought the bike dirt cheap with a melted piston, I opted for cooler running. Seem to go better too. Could be my imagination......

Title: Re: Engine staying hot for several hours after rid
Post by photojoe on 07/21/08 at 18:33:54

Stopped at the shop to get oil, and went back outside to the bike. standing there talking to my Girlfriend about my oil leak while smoking a cigarette, she put her hand a bit close to the pipe while pointing at the leak and I yelled, DON'T TOUCH THAT really loud. Had to give her a hug and kiss after that. Think I shook her up a bit, but better that than her finger melting on the pipe.

Title: Re: Engine staying hot for several hours after rid
Post by Sandy Koocanusa on 07/21/08 at 19:44:55

Yeah melted plastic is one thing, but melted finger is really hard to get off the pipe.

Title: Re: Engine staying hot for several hours after rid
Post by Dj12midnit on 07/21/08 at 20:21:14

I don't think the nickel will take that off.