What's the Proper Shutoff RPMs?

[leeave96 487]

I read somewhere that the Kohler Command engines used in today's lawn and garden tractors need to be shut-off at no lower rpms than 1800, half throttle. Failure to so can and has blown a head gasket.

Question is - what rpm are you supposed to shut down an Onan or Kohler K or Kohler Magnum engine on these Wheelhorses?

I've always idled down these engines prior to turning off, but this Kohler Command info has my wondering if what I'm doing is correct.

Thanks,

Bill

[bowtiebutler956 649]

I have never heard that before Bill. I wonder why? I've always run my K-301 down to idle before shutting it off, and I've never had a problem. The only command I've ever had was on a pressure washer, and it only ran at 3600, so that is how it was always shut off. Someone here probabaly knows more about this than I do.

Matt :flags-texas:

[Hodge71 663]

Its true, recommended shutdown for the Kohler Commands is half throttle shutdown. All of the Scag Zero Turns we have at my buddies lawn care business say so right in the manuals. They are all 27 thru 29 HP. I can tell you from watching guys when they dont do it...the backfire that it creates is quite un-nerving when you have a 120db explosion go off a foot behind your head. I'm not sure why the say it could blow the headgasket though. It pops thru the exhaust. I guess if conditions were perfect you could have a catastrophic explosion powerful enough to pop the head gasket. As far as our Thumpers and Magnums idling down is the way I have done it without any negative effects. I had my K 482 pop on shutdown this week but it was 98 degrees and I was pretty rough on it during its shakedown run. It worked quite hard for about an hour driving up and down the hills around my place to try to get the hydro to get hot.

[MarkPalmer 80]

Hodge71 posted the main reason why Kohler says to shut the Commands down that way- richer fuel mixture purging in to the hot exhaust when shutting down at idle often causes a loud backfire with Commands. This annoyance was ticking off a lot of Cub Cadet 2000 series purchasers, saying they didn't spend $3000 for a higher end tractor to listen to a junky sounding bang every time they shut it off. Kohler's answer is to shut the Command engines off while throttled up, which does seem to solve the issue. On the old cast iron singles, this didn't seem to be an issue and I never heard of shutting them down at idle causing head gasket problems so go ahead and idle down.

-Mark-

[pfrederi 17,206]

My 418 (Magnum 18) and my old Case VAC farm tractor both have to be idled down after working them or they will pop.... loudly , startled me really badly the first few times till I figured out how to avoid it by idling for a minute or so.

[Fordiesel69 236]

After a full load, a brief idle down to lower EGT's will have the same effect as an 1800 RPM shutdown. People are just too lazy to wait the 2-3 minutes,

Our older 16HP Twin Briggs lets out a backfire and a flame if you do not do this. And amazingly its not writen in any manual if it will not backfire either if you shutdown at half throttle.

[MalMac 1,328]

I agree with Fordiesel69 People are in just to big a hurry to let things cool down correctly. Good thing they are not talking about a big diesel here. Shut a big diesel down after it's been working hard without cooling it and see how many head gaskets and turbos you go through. I think even your small engines should be cool down before shut down, but that's just me. Kohler came up with that solution to prevent backfire and make all the customers happy. Wonder how happy they will be when they start getting premature engine problems. I wonder how many times engineers come up with solutions that are to make customers happy instead of whats really right for the proper function of the product.

Now with all that said I will talk out the other side of my mouth. I don't mean to knock all the engineers here and I do not have first hand about the proper shut down of the engine in question. I am just going by my own personnel experience and what I have been taught right or wrong.

[varosd 1,185]

I always let them idle and them shut them off. I then raise the hood to let everything cool down, then blow off all the dust/grass clippings (especially the Onan!) BTW I havent had to cut the grass since last week with all this heat...do have some clover weeds that I just weedwhacked down