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Old 09-16-2009, 06:52 PM   post #1 of 30
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Default start at full throttle or idle, engage deck at idle or f/t?

i've noticed some people leave their riding mowers/lawn tactors at full throttle all the time. even when starting. is this hard on an engine? i realise it's a much smaller engine but i would never start a car and immediately put the hammer down. i always way a short time and let the oil circulate. my riding mower has one of them throttle levers that you have to push past full throttle to choke when starting. i don't like the idea so i was thinking about installing a separate choke cable.

also is it good to engage and dis-engage the mower deck at full throttle or idle or half throttle? when i was growing up we had a 14 horse walmart murray and i always started in idle, ran up to full throttle and engaged the deck. as i got older and more aware of what was going on i noticed the belts would slip for a brief second when i did this. so i experamented. first i engaged the deck at an idle. well, the engine almost died. i found that about 1/4 to half throttle i could engage the deck then power up and the belts wouldn't slip.

does it even matter?

Last edited by tpolley; 09-16-2009 at 06:57 PM.
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Old 09-16-2009, 06:59 PM   post #2 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

I start mine at 1/4 to no more than 1/2 throttle and let it run a little bit before moving the throttle up more...for the fact that its a splash lube engine, and I want everything coated well before I start "work".

I don't know on the throttle to deck engagement. I have always flipped my PTO switch at full throttle, and never had a problem doing so. The engine will bog down some, which is to be expected, but as the deck gets spinning, everything mellows out to a nice tone, and away you go.

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Old 09-16-2009, 07:01 PM   post #3 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

I see your from Kansas, welcome! I'm out of Wichita where are you from?

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Old 09-16-2009, 07:35 PM   post #4 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

The guy next door to me builds Pontiac and Chevy (and on occasion Ford)race engines for a living. We got to talking about engine wear one day, and he was telling me that most start up damage is a direct result of a lack of oil, and not from expansion, and contraction. That is why new fuel injected cars such as the Ford Modular overhead cam engines rev upwards of 2 grand when first started. They are designed to rev high to ensure that oil is delivered to the overhead cams in a hurry. The only benefit that I can see starting a small engine at WOT would be to get immidiate oil pressure at start up. Its not a good idea to shut down an engine at WOT because internal temperatures could spike momentarily, especially on an air cooled mill.
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Old 09-16-2009, 08:00 PM   post #5 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

On the starting, half throttle is about best, however, if it has been sitting awhile I would start it at full for the first sec or two, is what i do, get that oil flow going is key, then afterwards idle it down.

On engaging/disengaging, some tractor/mowers Like my 93 craftsman actually says to have throttle to full for mowing, now as far as the actual engagement, half throttle atleast, for disengagement the same or less. Having the deck engaged puts alot of load on the engine, especially on the intial engagement, thats why its also I good idea to slowly engage the lever in, as opposed to just slamming it in, you want to gradually engage and disengage, that way you ease into the load and ease out of the load, it is better on the engine this way. Kinda like you clutch in and out of gear with a manual transmission.
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Old 09-16-2009, 08:12 PM   post #6 of 30
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Smile Re: start at full throttle or idle, engage deck at idle or f/t?

What does the manual say?
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Old 09-16-2009, 08:17 PM   post #7 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

Quote:
Originally Posted by tpolley View Post
i've noticed some people leave their riding mowers/lawn tactors at full throttle all the time. even when starting. is this hard on an engine?

also is it good to engage and dis-engage the mower deck at full throttle or idle or half throttle?

does it even matter?
These questions have been asked, and addressed, several times recently. I'm like you, I don't like the idea of starting an engine at full throttle, or even half, for that matter.

From the owner's manual for my '02 J-D GT235:

1-depress brake pedal
2-If engine is warm, leave throttle lever in "slow" position
3-Push and hold choke leverNote:choking may not be necessary when starting warm engine
4-turn key to RUN, check indicator lights
5-Turn key to START, blah, blah...
6-As soon as engine starts, release key.....release choke....put throttle lever in appropriate position

This is for an 18hp B&S engine.




From the owners manual for my '08 X748:
1-open fuel shutoff
2-depress brake pedal
3-Push throttle lever up to between 1/2 and fast position
4-turn key,5-check indicators, wait for preheater (diesel)
6-crank engine.....etc

for a Yanmar diesel

From what others said, the V-twin gas engines is much the same. My dealer started mine up at about 2/3 throttle, and shut it off the same way.

My thoughts are, if the engine oil pump sufficiently lubes the engine when it is running at idle, then it should also provide enough oil at start-up at idle. If the engine is used fairly frequently, like every other day, or thereabouts, there should be enough residual oil in the galleys and bearing surfaces to provide an immediate supply when the engine starts up, regardless of engine speed. But if the engine has sat unused for an extended period, more of this residual oil may have drained due to gravity. Nevertheless, if the oil pump is in good condition and clearances are nominal (close to normal), then oil will start to move as soon as the engine is cranking.

So maybe it doesn't matter either way. I know that I won't start mine at full, or even half throttle, I usually crack it just a bit above idle.

As far as engaging the deck, I start the deck at full throttle, which is also what the manual recommends. The HST in my 748 has internal clutches , but my GT235 is the electric variety, and it at least needs a good bit of rpm's so it doesn't stall the engine
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Old 09-16-2009, 09:39 PM   post #8 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

I'm going to cotradict what's been written here. The manual for my Craftsman 24hp v-twin Briggs Tractor says to start and stop the tractor at full throttle.

Secondly, I have read many times on this forum to drop the throttle as low as possible before engaging attachments to save wear on the belts and the (expensive) electric PTO. My Berco snowblower manual also recommends this. Basically you want the throttle as low as it can be without stalling the engine for attachment engagement (about 1/4 to 1/2).

It's funny, my JD 316 Kohler manual says to drop the throttle all the way down for 30 seconds before shut off to avoid backfiring. My Craftsman manual says keep the throttle wide open to avoid the same problem!
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Old 09-16-2009, 09:41 PM   post #9 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

start/shut off at WOT, and engage the deck at WOT. never had a problem with it.
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Old 09-16-2009, 10:36 PM   post #10 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

Every tractor/engine maker has its own requirements for each of its versions...you do what the manual says...for starting, stopping and PTO engagement
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Old 09-16-2009, 10:57 PM   post #11 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

For what I no about mechanic (25 years so far) a pressurize oil system on engine as to build up pressure in a few millisecond whit oil filter full and no more of 1 second whit filter empty.

My 2 cent
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Old 09-16-2009, 11:05 PM   post #12 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

Keep in mind what technology you are talking about.

1) Carburated engine thats reving like mad when shut off will continue to turn for a while before it stops. During this time you are still sucking gas into the cylinder and out the exhaust its just not getting any spark. Try this at wide open throttle and turn the ignition back on before it stops turning and you mide get a loud bang that would be the unburnt gas exploding with the next exhaust cycle. (Not good for your machine)

2) Fuel injected models will just stop pumping gas into the cylinder regardless of how fast the engine is spinning if you turn off the key. If you try the above procedure you should not get the bang.


As for what I do. I believe in low throttle let it warm up a few seconds. give it a little more throttle, then a little more etc.

For the PTO I engage at lowest possible throttle then increase throttle.

And I have one question.

In the JD318 operators manual it says not to let the engine idle for prolonged periods as it may not get enough cooling air and overheat the engine. So I wonder what is the best compromise between not working the engine too hard and making sure it is pushing enough air past the fins?
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Old 09-16-2009, 11:05 PM   post #13 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

Quote:
Originally Posted by GR8racingfool View Post
I see your from Kansas, welcome! I'm out of Wichita where are you from?

~F~
thanks for the welcome. regretfully i'm in lenexa with no yard to mow (appartment). my rider is stored at my dads (the only thing i store there that he doesn't complain about). hopefully in the not too distant future the wife and i will have a nice big yard to maintain somewhere south of here.
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Old 09-16-2009, 11:32 PM   post #14 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

The oil is going to take the same number of pump turns to lube the motor.
Do you really think it's better for your engine to get to full rpm before then?

I can't think of any good reason to engage any type of clutch or belt at WOT.
Same with shutting down.
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Old 09-17-2009, 06:28 AM   post #15 of 30
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Default Re: start at full throttle or idle, engage deck at idle or f/t?

This is almost 40 years old and has been in the family since new.

It has NEVER been started at full or even half throttle during it's lifetime. It still runs perfect and only uses about a half pint of oil in 12 hrs of running at half throttle. The engine has never been apart! Seems like every one has his or her own way of doing things and no amount of talking can change that. Some people even say "I never change my oil, I just add more". Their the ones who usually complain that their mower is junk and they'd never buy that brand again! Oh well, to each his own.
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