start at full throttle or idle, engage deck at idle or f/t? [Archive] - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information

: start at full throttle or idle, engage deck at idle or f/t?


tpolley
09-16-2009, 06:52 PM
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?

GR8racingfool
09-16-2009, 06:59 PM
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.

~F~

GR8racingfool
09-16-2009, 07:01 PM
I see your from Kansas, welcome! :MTF_wel: I'm out of Wichita where are you from?

~F~

saleen49
09-16-2009, 07:35 PM
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.

Tractor Master
09-16-2009, 08:00 PM
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.

MarkTroy
09-16-2009, 08:12 PM
What does the manual say?

KHodges
09-16-2009, 08:17 PM
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

ggsteve
09-16-2009, 09:39 PM
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!

davidg
09-16-2009, 09:41 PM
start/shut off at WOT, and engage the deck at WOT. never had a problem with it.

Upper5Percent
09-16-2009, 10:36 PM
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

stladrill
09-16-2009, 10:57 PM
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

tractorpilot
09-16-2009, 11:05 PM
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?

tpolley
09-16-2009, 11:05 PM
I see your from Kansas, welcome! :MTF_wel: 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.

PartsManBarr
09-16-2009, 11:32 PM
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.

Paul J
09-17-2009, 06:28 AM
This is almost 40 years old and has been in the family since new.
http://i58.photobucket.com/albums/g273/PJ161/Tractors/001.jpg
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. http://i58.photobucket.com/albums/g273/PJ161/A-Icons/cool0041.gif

m.jodrey
09-17-2009, 07:00 AM
I have never engaged the mower at full throttle on any I've ever owned.Half throttle then ease on up.

thendricks
09-17-2009, 07:18 AM
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.

I have heard similar to the above. I dont really follow this with my tractor, i start it at just above idle (1600 rpms on a yanmar deisel). I dont think i will put enough hours on it to matter really.

Thad

Nouveau Redneck
09-17-2009, 07:37 AM
As others have stated, different engines, or even the same engine used in different tractors, may have different design requirements. Follow what the manual says, especially during the warranty period, as improper usage can void the warranty.

*chris*
09-17-2009, 12:18 PM
I read the ENGINE manual, not the TRACTOR manual.

For my Kohler 26hp Courage I start at half throttle with the choke always (hot and cold) and let it idle for 30-60 second before shutdown.

As far as the PTO, I always enable the PTO at full throttle as the TRACTOR manual states, there is not good reason to bog the engine at low throttle to "save" the PTO clutch.

I also cut at full throttle so I get maximum speed and best bagger performance.

Chris

Nouveau Redneck
09-17-2009, 01:08 PM
I read the ENGINE manual, not the TRACTOR manual.

....

I always enable the PTO at full throttle as the TRACTOR manual states

If you read the ENGINE manual, and not the TRACTOR manual, how do you know what the TRACTOR manual states about the pto?

Also, your warranty is with the manufacturer of the tractor, not the manufacturer of the engine. The one that offers the warranty is the one that can disallow your warranty if you didn't follow their instructions.

*chris*
09-17-2009, 01:41 PM
....



If you read the ENGINE manual, and not the TRACTOR manual, how do you know what the TRACTOR manual states about the pto?

Also, your warranty is with the manufacturer of the tractor, not the manufacturer of the engine. The one that offers the warranty is the one that can disallow your warranty if you didn't follow their instructions.

Try reading my post again slowly.

PartsManBarr
09-17-2009, 04:00 PM
there is not good reason to bog the engine at low throttle to "save" the PTO clutch.


What harm is caused by "bog"ing your engine that is worth burning up a clutch over?
Engaging the clutch at higher rpm and power WILL wear it out faster.

ejbpesca
09-17-2009, 04:13 PM
My little Craftsman cranks in two seconds on full throttle then I immediately take it down to quarter throttle. Once it is warmed up a bit I push the throttle to a notch it has for the correct mowing rpms which seems to be about 3/4 throttle. Then I engage the blades.

This inexpensive 2000 series has run flawlessly for six years and with a belt inspection done by Sears a couple months back they said they were like new! Finally got a set of new blades after six years.

They had worn so evenly there was never an abnormal vibration from them but the 42 in. cutting path had been brought down to about 30!

I've got more questions than answers so I'm going to give it a go.
jb

m.jodrey
09-17-2009, 04:47 PM
Total agreement with PartsManBarr on the pto.

C2H8O
09-19-2009, 12:05 AM
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.
That had not occured to me. It seems like a good idea. I have been running WOT all the time even when starting the attachments and I have noticed a huge jerk and strain on the belts.

My older Bolens suggests WOT for running the attachments, it does not say anything about engaging them. I'll try lower throttle at engagement.:thanku:

davidg
09-19-2009, 12:11 AM
funny but the electric PTOs are the SAME as a A/C compressor clutch on a car. how long do those last and most engage hundreds of times a day at all sorts of engine speeds from idle to 4-5k! all my machiens the manual says to both engage AND USE the PTO at WOT.

Tractorpilot, this is why many newer machines have solenoids on teh carb bowls, it shuts gas off BEFORE spark is killed to prevent a backfire. if your machien has this, no need to worry about it.

some engine/tractor manuals DO say to shut back before shutting down, though mine do not. but nearly every one says go to 3/4 or full throttle and choke as needed to crank. as was stated, read the manual for your machine.

pfreiburger
09-19-2009, 12:44 AM
For my GT2550 both the Cub operators manual and the Kohler engine manual say to use 1/2 throttle when starting. The Cub manual also states to engage the PTO at 1/2 throttle.

For years I have always started at full throttle and engaged the PTO at full throttle, but it makes sense to use half throttle, particularly concerning the PTO engagement.

I am going to attempt to use half throttle at these times, but I am an old dog and don't always do well with new tricks!

Ingersoll444
09-19-2009, 06:50 AM
I always start about 1/2 throttle, and shut off at low. With the old Kohler K's you NEED to let it spin down before you shut it off, or your going to scare everyone in two countys away!! "BOOM!!!" :D

As for the PTO.. manual ones I try to keep about half or a little more. Fast enough to have enough power to pull the load, but not full. Not all the time though. If I have to shut it off wile mowing, I just leave it full speed, and reengage. As for elect PTO's? I engage them at full speed. All I have used seem to draw a LOT of elect power from the engine, and then engage so fast anyways, I doupt you will see any premature wear.

markwb
09-19-2009, 07:17 AM
Maybe we oughta send this one to MythBusters. :)

jgd
09-20-2009, 08:23 PM
Anyone bump their PTO to slow start and then give it a full start?