What RPM Settings do you guys recommend for a Kohler CV16S? - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 25 Old 10-11-2019, 06:47 PM Thread Starter
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What RPM Settings do you guys recommend for a Kohler CV16S?

Howdy All,

I have a 217.271110 model Craftsman Riding Mower with the Kohler Command 16.5 HP engine that was recently given to me. I just gave the engine a tune up and have a question as to what the RPM settings at idle and for high speed should be. The Craftsman manual and Kohler Manual say two different things. The Craftsman manual states that the idle should be set at 1,750 RPM's, however there is no mention of the "No Load" High speed RPM other than it has been factory set. The Kohler manual recommends that the idle should be set to 1,200 RPM's and that the "No Load" High speed RPM should be set at 3,750 RPM's but to refer to the manufactures instructions for specific info. So now what?
My idle speed was found to be 1,500 RPM's so I bumped it up the Craftsman manual spec of 1,750 RPM. The "No Load" High speed RPM was found to be around 3,100 RPM. I felt that seemed a little low and bumped it up to 3,500 RPM.
What do you guys think about those RPM numbers?

Hec

Last edited by Hec In Omaha; 10-11-2019 at 07:18 PM.
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post #2 of 25 Old 10-11-2019, 09:34 PM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Different engines are governed to different depending on the application.
When your blades disintegrate you'll understand why. 3100 probably was pretty close to correct.
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post #3 of 25 Old 10-12-2019, 02:12 AM Thread Starter
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I don’t think my blades are going to fly apart by raising the RPM 400 RPM’s. Besides my 3,500 RPM setting is less than the max setting specified by 2,750 RPM’s so the engine isn’t in any danger of over-revving. It’s reasonable to believe that after 21 years the idle and fast speed setting may be off. Already found that to be true with the idle setting being lower than what the Craftsman manual specifies. The 16.5 HP rating that’s pasted on the tractor is achieved at 3,600 RPM according to the Kohler manual. So why would Craftsman lower the Fast No load RPM’s to 3,100 RPM’s? At 3,100 the engine probably develops less than 14 HP. Doesn’t make sense to me. My 1978 John Deere 210 No load fast setting is set to 3,600 RPM’s. No problems blowing it’s deck blades apart. Blade speed is the key to a good cut.

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post #4 of 25 Old 10-12-2019, 03:02 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

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Originally Posted by Hec In Omaha View Post
I donít think my blades are going to fly apart by raising the RPM 400 RPMís. Besides my 3,500 RPM setting is less than the max setting specified by 2,750 RPMís so the engine isnít in any danger of over-revving. Itís reasonable to believe that after 21 years the idle and fast speed setting may be off. Already found that to be true with the idle setting being lower than what the Craftsman manual specifies. The 16.5 HP rating thatís pasted on the tractor is achieved at 3,600 RPM according to the Kohler manual. So why would Craftsman lower the Fast No load RPMís to 3,100 RPMís? At 3,100 the engine probably develops less than 14 HP. Doesnít make sense to me. My 1978 John Deere 210 No load fast setting is set to 3,600 RPMís. No problems blowing itís deck blades apart. Blade speed is the key to a good cut.

Hec
Two reasons.

- The government mandated maximum tip speed of the mower blades.

- The transmission manufacturer's maximum rated input rpm for the particular transmission installed in the tractor.

The mandated tip speed is close to 200 mph. That's the velocity that can be imparted by the blade when ejecting a projectile. Do you really want it travelling even faster?

While the blade may not self destruct, they have been known to bend severely, or even break, when hitting immovable objects. An out of balance blade spinning at excessive rpm can do severe damage to the mandrel holding it, and to the deck shell when the mandrel breaks, if you can't shut it down in time.

Exceeding rated input rpm on a hydro risks damaging or destroying the rather expensive hydro. Cavitation is one of the risks, and that can destroy a hydro in seconds in the right (or wrong) circumstances.

I can only think of four hydros that were rated for more than 3450 input rpm, and none of them are a current option. Only one of those was rated for more than 3600 rpm, and it was too expensive for Craftsman to install in their top of the line FF Series GTs to meet the price point desired.

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Last edited by TUDOR; 10-12-2019 at 03:26 AM.
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post #5 of 25 Old 10-12-2019, 04:41 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Blade speed is often misunderstood. Once the tips go supersonic all kinds of bad things can happen.

Sharp > speed.

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post #6 of 25 Old 10-12-2019, 09:49 AM Thread Starter
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Thanks everyone for chiming in!

My tractor has a manual 6 speed transaxle so the issues with hydrostatic trannys don’t apply here. I also realize that the engines RPM will drop when the blades are engaged.
I did not know about blade tip-speed regulation. Wouldn’t be hard to calculate the blade tip-speed and go from there. You would think given the mentioned blade tip-speed requirement, that the Engineers would limit the speed of the blades via the deck/PTO pulley sizes knowing what the engine RPM needs to be to develop full power. This way the engine realizes max power and the required blade tip-speed is maintained. This is how power equipment rotating speed is controlled on belt/chain driven equipment . Now equipment directly driven off the motor shaft is another story and speeds have to be controlled by the motor/engine.

Looks like I need to research this some more.

Hec

Last edited by Hec In Omaha; 10-12-2019 at 09:59 AM.
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post #7 of 25 Old 10-12-2019, 11:04 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Unless you're in the habit of mowing thick, tall, and/or wet grass at high travel speeds, you don't need 16 hp for a mower less than 50" wide. A Swisher 60" tow behind mower comes with a 14.5 hp engine.

At the top speed of lawn tractors, and the mandated tip speed, each blade of grass has 6-8 possibilities of meeting up with the outer 3" or so of the blade where the cutting edge is located. If you can't cut it with 6-8 tries, another 1 or 2 isn't going to help. You either need different blades or a different deck.

Manual transmissions are also subject to maximum input speeds. Most LTs have a top speed of about 5.5 mph.

Maybe the Engineers actually know what they are doing. They have to work within government regulations, supplier specifications, space limitations, and bean counter demands, and they've been doing it, more or less successfully, for over 60 years.

Bob

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post #8 of 25 Old 10-12-2019, 11:56 AM Thread Starter
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Yes the Engineers know what their doing, however they should provide the No Load Fast RPM setting in the event it becomes out of out of spec. This tractor will be bagging most of the time and I want ensure all is set properly.

Hec
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post #9 of 25 Old 10-12-2019, 06:56 PM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Quote:
Originally Posted by Hec In Omaha View Post
The Craftsman manual states that the idle should be set at 1,750 RPM's, however there is no mention of the "No Load" High speed RPM other than it has been factory set. The Kohler manual recommends that the idle should be set to 1,200 RPM's and that the "No Load" High speed RPM should be set at 3,750 RPM's but to refer to the manufactures instructions for specific info. So now what?
My idle speed was found to be 1,500 RPM's so I bumped it up the Craftsman manual spec of 1,750 RPM. The "No Load" High speed RPM was found to be around 3,100 RPM. I felt that seemed a little low and bumped it up to 3,500 RPM.
What do you guys think about those RPM numbers?

Hec
Note that I'm not arguing against your reasoning. I'm merely explaining aspects in order to add clarity and understanding to the situation.

The Kohler specs are for the engine to cover all applications. End use manufacturers are free to use any speeds that fall within Kohler's specified speed range. Tractors are not the only application. The engine may also be used to power water or hydraulic pumps, portable sawmills, generators, cement mixers, etc., etc., each with a different high, and/or low, idle requirement. The Craftsman specs are for the limitations of the various implements that can be attached to the tractor, as well as for the transmission.

If you clean the governor components (flywheel fan, air vane) to ensure "as new" air flow and replace the governor spring due to the possibility that it has been stretched or weakened, it should result in the "as designed for the specific tractor" high idle, unless different linkage holes have been used to change the original setting.

I have seen comments quoting specs for other L&G tractors with high idle speeds ranging from 2800-3600 rpm, and some generators have a high idle of only 1800 rpm. If you dig deep enough, you can usually find the reasons for the differing high idle rpms.

Two of the things that I don't mess with without a thorough understanding of the effects on other components are governors and hydraulic relief valves. In both cases, excessively high numbers sooner or later result in broken parts.

Bob

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Last edited by TUDOR; 10-12-2019 at 07:02 PM.
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post #10 of 25 Old 10-13-2019, 11:59 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Doubt it makes a whole lot of difference. If mowing and you run into some thicker organics, as long as the rpms are in the range, and the throttle spring can go to WOT when the governor relaxes, it won't make a lot of difference.
As far as the low-speed idle, I don't give a whit for the most part, as I don't run the engine at those rpms, even though both have 'full pressure, filtered' systems.
The natural tendency is to 'baby' the engine. For a long time, that's what I thought, and did, as I wanted to be kind to my equipment. I was informed by an old geezer I worked with who had years of farm experience(one of my best friends) that I should fire it up, and run it at the full rpms allowed. Period. He's been gone for almost 20 years, but he was an education all in himself.
Anyway, I followed his advice and have been pleasantly surprised. I have not even looked for an idle adjustment on either machine. IDK. Start, ease in the load after a few minutes travel to the 'cutting area', and just keep going. Be sure to check the oil every start, and change it as needed. If it smells bad, it's likely bad.
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post #11 of 25 Old 10-13-2019, 04:05 PM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

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Doubt it makes a whole lot of difference.
Food for thought. The engine speed was bumped up 11%. The engine also powers the attachments like the mower and a snow thrower/blower. You can sometimes drive a car at 50 mph with unbalanced tires and still have a smooth ride. Bump the speed up 10% and the resulting vibration just may shake the fillings out of your teeth.

A bad drive shaft universal will do the same thing with a mere 10% increase in rpm. A drive shaft in a V-8 truck turns at about 1300 rpm at 50 mph in overdrive.

Yes, an 11% increase in rpm can make a difference. I'm not saying that it will, only that it can.

Bob

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Last edited by TUDOR; 10-13-2019 at 04:23 PM.
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post #12 of 25 Old 10-14-2019, 04:55 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

FWIW, I removed the engine (CV15S) from an older Craftsman (917.252610) last year. This past week I put it on a Deere Lt155. I checked the RPM after I got it installed and it was about 3100. Raise the RPM if you want to but you probably don't need to.
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post #13 of 25 Old 10-14-2019, 10:26 AM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

Can could should Shall will would May might must.

Yup.

It can make a difference when you are close to the limit of power being developed. I think, in 9X% of the use, the engines on these are not working close to their limit.
If, OTOH, you are pulling a scraper and pushing a plow, you may need all the power that can be developed. No question. Totally can use it all. In that 5-10% of the use.
In my limited experience, not having a front loader, plow, sprayer, or snow blower, just a mowing deck, the engine does not work hard for a very high percent of the time, and more hp and torque would not be missed. For a 42" deck, 12-14 hp is adequate, for 99% of the use.
If you know the use, you can pretty much be certain whether you can cut back from the over-powered "Look, Billy, this one has 26.225 HP! That's a full 1.2 more than that one, and it only costs $25 more." sales brochure touting of 'features and benefits'. Do note that all the 'negatives and misses' are not on that brochure or placard.
It depends.(whether you need an exact replacement or can step down)
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post #14 of 25 Old 10-14-2019, 06:07 PM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

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It can make a difference when you are close to the limit of power being developed. I think, in 9X% of the use, the engines on these are not working close to their limit.
If, OTOH, you are pulling a scraper and pushing a plow, you may need all the power that can be developed. No question. Totally can use it all. In that 5-10% of the use.
In my limited experience, not having a front loader, plow, sprayer, or snow blower, just a mowing deck, the engine does not work hard for a very high percent of the time, and more hp and torque would not be missed. For a 42" deck, 12-14 hp is adequate, for 99% of the use.
Nope. You don't need all the power available. My MF1655 pulled a 5' back blade at the same time as it pushed a 54" bucket through up to 24+" of fresh snow at a 2/3 throttle setting for years. With 400 lb of ballast plus operator and chained tires, it would lose traction long before it could run out of horses. At that point, the back blade was raised to add another 250 lb of counterweight to the equation and it continued on its merry way.

When pushing/pulling snowflakes, the number one restrictor of capability is traction! It takes more weight than the tractor is rated for to gain enough traction on snow to require a serious percentage of the power available.

Note that there are only one or two hydro transmissions that can deliver enough horsepower to the drive axle to stall a 16 hp engine on a straight pull or push, and you won't find either in a Craftsman.

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post #15 of 25 Old 10-14-2019, 06:44 PM
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Re: What RPM Settings do you guys recommend for a Kohler CV16S?

"Me thinks a mountain has been made out of a mole hill"

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