Do You Throttle All The Way Down Before Turning Off The Engine?

Or, when you quit mowing, do you shut down the engine at full throttle and not concern yourself about it?

My old tractor style 46" deck, Craftsmen, powered by a 24 Hp, B & S Intek engine's manual never mentioned having to do this. So, I always left it going full blast when I killed the engine. I sold it to my next door neighbor with 350 hours on it and he is now running it with over 500 hours on it and he doesn't worry about shutting it down at idle.

My Toro manual says to idle all the way down, wait a minute and then turn off the engine.

What do you guys say?

Zeroturner said:

Or, when you quit mowing, do you shut down the engine at full throttle and not concern yourself about it? My old tractor style 46" deck, Craftsmen, powered by a 24 Hp, B & S Intek engine's manual never mentioned having to do this. So, I always left it going full blast when I killed the engine. I sold it to my next door neighbor with 350 hours on it and he is now running it with over 500 hours on it and he doesn't worry about shutting it down at idle. My Toro manual says to idle all the way down, wait a minute and then turn off the engine. What do you guys say?

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Didn't do on my rider for 26 years because manual didn't say. Now I just do it because my zero turn manual says so. I just stick with manual.

Absolutely, at least 30 seconds at low idle before shutting down. I can't recall hearing or seeing anyone press their vehicle gas pedal to the floor and holding it before switching the the key to off.

Zeroturner said:

Or, when you quit mowing, do you shut down the engine at full throttle and not concern yourself about it?

My old tractor style 46" deck, Craftsmen, powered by a 24 Hp, B & S Intek engine's manual never mentioned having to do this. So, I always left it going full blast when I killed the engine. I sold it to my next door neighbor with 350 hours on it and he is now running it with over 500 hours on it and he doesn't worry about shutting it down at idle.

My Toro manual says to idle all the way down, wait a minute and then turn off the engine.

What do you guys say?

Click to expand...

I idle all the way down on my GS because like DSepe said the manual say to. I've always idled down on all my mowers before shutting off.

I too follow the manual, but I wonder why it's necessary?

Some I idle down just because I don't like shutting them off at full throttle. Push mower engines are shut off at full throttle every day since there is no throttle control. Some engines like Kohler have to shut them down at full throttle due to the design of the carb that will cause afterfire if shut down at idle.

Always idle down. Always try to tell our customers with riding units to do the same, as most don't read the manuals. Engines manufactures tell us that the reason is to reduce the amount of unburnt fuel which enters the engine and then the atmosphere. I don't really believe them but do pass it along if they customer asks why.

I've retired from industrial engines that always shut down at full throttle when un-attended. 1,000 HP to 2,000 HP it made no difference. Briggs Vanguard, regarded as one of the best small engines, always starts at full throttle and shuts down at full throttle on many applications.

My lawn tractor, always at low idle rpm unless a swarm of bumble bees are after me then I bail and run the best I can and to hell with that tractor.

So I suggest either way, what ever makes you happy.

On walk-behind mowers, there is no genuine need or benefit to slowing the engine down before shut-down. One marginal exception would be a mower with a flywheel brake (engine and blades both stop when you let go). If you reduce the engine speed before shut-down on this type of mower, it could fractionally reduce the wear on the flywheel brake pad(s) ever so slightly. It is an insignificant amount.

Other mowers with blade brake clutch (only blades stop when you let go) usually have the engine stop switch built into the throttle control, so you have to move it from FAST to SLOW before getting to STOP anyway. No flywheel brake pads on these models, so no benefits to slowing the engine before shut down.

Most walk-behind mowers have gravity-feed fuel systems, so the fuel pressure is very slight into the carburetor, and the chance of backfire from excessive unburned fuel getting into the engine is quite rare.

Many modern walk-behind mowers don't even have a throttle control, and run wide-open at start and stop. Extensive testing has shown such fixed-throttle designs do not cause cause any shorter engine life or operational problems (at least not here at Honda). In fact, warranty data reveals the absence of throttle controls and cables actually reduced overall repair frequency caused by damage to the throttle control cable from kinks, snags and stretching/wear.

For riding equipment that uses a fuel pump, the fuel pressure to the carburetor is higher, and to prevent backfiring, many engines have a fuel-cut solenoid/valve that instantly cuts fuel flow when the engine is switched off. So it does not matter (as far as backfiring risk goes) to reduce the engine speed or not.

Thanks to everyone for your helpful/educational information.

I'm still learning...