Letting it idle

[CCW 1,292]

My 89 312-8 is only used occasionally when moving my trailer around the yard as I cut the grass with a regular lawn mower and grass catcher.  Cuttings are dumped into the trailer.  Instead of turning off the tractor all the time I let it idle while I mow to completely warm up the engine.  I am looking for opinions on whether I should let it idle the 30 minutes until the next dumping of the trailer when it is fully throttled of should I shut it down.

[ebinmaine 67,265]

There are those that will NEVER let an air cooled engine idle other than right before shutdown.

 

Air cooled engines need airflow and most are splash oil lube systems as well.

We don't ever let ours set at less than 40 to 50 percent throttle.

 

Also, it's just a use of fuel to let it sit like that.

 

Start it.

Warm it up for 3 to 5 minutes. Use it...

Shut her down til next use.....

[kasey54 305]

For what its worth , I may  one day pay the price,.. I have 2 tractors I till with, hours at a time at just above idle. One is a 10 hp briggs, the other a 10 hp Kohler.  I check oil etc, neither has ever seemed over heated at all. I till low gear  as slow as i can. I feel it saves wear on the tines in my very sandy soil, they sip the fuel , and the tiller digs deeper.

[ebinmaine 67,265]

1 minute ago, kasey54 said:

 above idle

There's a key there.

 

 

[kasey54 305]

True, but it,s a low idle. nowhere near 1/4 throttle.

[clueless 2,975]

Kohler flathead engine are cooled by air and the oil inside it. The lower the RPMs the less air is blowing on it to cool it and the oil is not circulating as fast, neither are good for an air cooled engine . I think Kohler recommends WOT when running. A few years ago I ran a 12 hp at full throttle for few minutes and checked the temp of the head and the side cylinder fins with my digital thermometer, then ran it at idol for the same length of time and checked the temps again. I don't remember the exact numbers but the temps at idol were way higher then at full throttle . Other than saving a little gas, no real reason to run it at low RPMs, run that thing a full throttle, that's what it's built for .

[953 nut 55,059]

          I'm with EB and Chris on this. Splash lubrication needs to be given every opportunity to do it's job and the lower the RPMs the less splash is occurring. When plowing snow I will change gears or slip the clutch rather than engine speed while plowing in tight areas.

[wfrpalm 218]

I wouldn't let anything idle for 30 minutes let alone something air cooled, i think you are tempting fate.

[CCW 1,292]

Good input.  Today was cool, only 50 degrees.  But splash lube I had not thought of.  Thanks.

[Digger 66 3,478]

3 hours ago, ebinmaine said:

 

Start it.

Warm it up for 3 to 5 minutes. Use it...

Shut her down til next use.....

 

Precisely . 

Long term idling does nothing positive .

[pfrederi 17,660]

Most important is idle speed.  Kohler says 1250 a lot faster than liquid cooled oil pump engines...

[CCW 1,292]

Idle no more. Took all of your comments and yesterday I fully warmed up the horse and shut down between runs.  Thanks for the input.

[pacer 3,168]

This is one of those topics that would never get a full agreement on (like which is the best oil?) At my 80yrs old point and having ran small engines since I was 9-10yrs old, I probably do both. On the - rare - occasions that I need WOT I'll use it, if not I set the throttle to be convenient at the time. My D160 'yard' tractor is used to haul around a trailer picking up limbs, etc in the yard and its always set at just enough throttle to put-put around on. Cutting grass I'll run at whatever is needed for the grass at the moment, in a lot of my yard I'm 'cutting dirt' mostly and I bring the throttle back there.

 

Another factor here is that there really isnt any WOT throttle setting, not on a properly governed engine. On my 5 engines the Onan reaches the highest rpm and I'm guessing that is only 25-2800rpm. The Kohler 341's might get 20-2200rpm. If you ever doubt that set the throttle open and reach over and manually move the arm at the carburetor - quite an increase.

 

In no way am I arguing the points here about the cooling of these engines, they are valid points, but I have to wonder just HOW critical it is to strictly adhere to.

 

The original posters letting it idle for 30 mins is no doubt pushing the limits a bit........

[adsm08 2,022]

In my experience, with an air cooled engine actual movement is just as important as engine speed.

 

You can't take an air cooled engine, that has no real cooling fan, and let it sit and run at any RPM in the exact same spot, and expect it to not get over-temp. That is the equivalent of letting a water cooled engine run with the water pump not running.

 

You can even use yourself as an example, run on a treadmill for 10 minutes. Then run down the road for 10 minutes. Where did you sweat more?

[ZXT 2,401]

27 minutes ago, adsm08 said:

 

 

You can't take an air cooled engine, that has no real cooling fan, and let it sit and run at any RPM in the exact same spot, and expect it to not get over-temp. That is the equivalent of letting a water cooled engine run with the water pump not running.

 

That's not exactly true. The cooling fins are quite literally a cooling fan... and on something that isn't water cooled or doesn't have a forward facing duct directing air towards the engine, moving isn't going to help a bit. Besides, 3 MPH isn't fast enough to generate any real amount of air over the engine.

 

If sitting still or moving very slowly created a cooling problem for these engines, they wouldn't have used them on stationary air compressors, generators, trenchers.. etc.

[Tuneup 1,433]

I've been told and it makes perfect sense, that the cooling capacity of the engine is designed for adequate cooling at max RPM under significant load. Once the job is done, running unloaded at max RPM for a minute should cool it down. Would that make cooling at above idle under load adequate? Maybe or maybe not...