12 hp carb on a 16 hp ?

[ebinmaine 72,719]

Given the fact that I never ever run my engine at Full Throttle is it okay to use a 12-horse kohler carb on a 16 horse engine?

I do realize that they are a smaller carburetor.

As it happens I have a couple of 12 horse carbs sitting on the shelf but nothing from a 14 or 16 horse.

 

Just wondering how it would work and what if any would be the detrimental effects?

[JoeM 8,347]

I have put a 12hp one on a 14 ran great.

[Tractorhead 9,212]

It shall work, at idle and at midrange and also at 3/4 Throttle.

just in max throttle you will maybe lost a plenty of Power.

 

It depends on volume- Airstream, what can passed thru carb, it can be there is no powerloss.

it‘s worth a try.

 

but if the Carb bore inside is much smaller, you maybe need an adapter to fit.

If you found an smallcarb Adapter to mount, make an funnel to the Intake of the engine.

to reduce a bit the whirls.

Edited April 22, 2019 by Tractorhead

[oldredrider 2,553]

FYI ...Kohler K series are meant to be run wide open. High rpm's provide the best cooling ( it IS an air cooled engine) and internal lubrication, as they are NOT oil pressurized engines.

It's your engine and you can run it any way you want but, for longevity, Kohler knows best.

[pfrederi 18,689]

8 minutes ago, oldredrider said:

FYI ...Kohler K series are meant to be run wide open. High rpm's provide the best cooling ( it IS an air cooled engine) and internal lubrication, as they are NOT oil pressurized engines.

It's your engine and you can run it any way you want but, for longevity, Kohler knows best.

 

 

I have heard this argument before but I do not fully agree with it.  There are some pieces of equipment that use air cooled splash lubed engines that recommend half throttle for operation (Jari Sickles) for one.  it is usually recommended to idle down after hard use a to let the engine cool down before shutting down.

I think the bigger issue is idle speed.  most of us tend to set it by ear and it is probably to low.  your car of that vintage probably idled at 5-600 RPM  Kohler specifies 1250 for idle speed which sounds pretty fast but they must know what provides adequate splash and cooling.

Edited April 22, 2019 by pfrederi

[ebinmaine 72,719]

9 minutes ago, oldredrider said:

FYI ...Kohler K series are meant to be run wide open. High rpm's provide the best cooling ( it IS an air cooled engine) and internal lubrication, as they are NOT oil pressurized engines.

It's your engine and you can run it any way you want but, for longevity, Kohler knows best.

 

3 minutes ago, pfrederi said:

 

 

I have heard this argument before but I do not fully agree with it.  There are some pieces of equipment that use air cooled splash lubed engines that recommend half throttle for operation (Jari Sickles) for one.  it is usually recommended to idle down after hard use a to let the engine cool down before shutting down.

I think the bigger issue is idle speed.  most of us tend to set it by ear and it is probably to low.  your car of that vintage probably idled at 5-600 RPM  Kohler specifies 1250 for idle speed which sounds pretty fast but they must know what provides adequate splash and cooling.

 

 

 

I've been around small engines of various types my whole life. When I first got a Wheelhorse 3 years ago I was really not at all familiar with this brand.

I had only had one or two Kohlers in my possession over the years.

Because of the fact that I am the type of person that really loves to over-analyze things times about 15 and then figure out what I need to do, I did a ton of reading and research and of course have asked all of you folks a million times over. And a  lot of other sites. We also have a very good friend who has done a lot of small engine maintenance in the past.

The conclusion that I have basically been led to is that most air-cooled small engines should be at 80% to 100% throttle if you are running an Implement of any kind OR if you are running a hydro transmission.

All of our tractors are Gear Drive. We have 0 implements at this time.

 

My research has led me to believe .... and I may not be quite right. Don't get me wrong here. .....

My research has led me to believe that a Gear Drive Machine's engine can and should be run somewhere in the 50% to 60% throttle range at bare minimum. 70% to 80% could be considered better by some.

 

[oldredrider 2,553]

Not to start an argument, especially with a member I fully respect, a sickle bar DOES require a lower RPM. 

However, most implements require a high RPM to operate efficiantly. 

[ebinmaine 72,719]

Just now, oldredrider said:

Not to start an argument, especially with a member I fully respect, a sickle bar DOES require a lower RPM. 

However, most implements require a high RPM to operate efficiantly. 

Ahhh......

Very nice.

 

No argument started here. That's a new one to me but I've never had a sickle bar mower.

 

[cschannuth 3,817]

50 minutes ago, oldredrider said:

FYI ...Kohler K series are meant to be run wide open. High rpm's provide the best cooling ( it IS an air cooled engine) and internal lubrication, as they are NOT oil pressurized engines.

It's your engine and you can run it any way you want but, for longevity, Kohler knows best.

 

I agree to an extent but I'm pretty sure Kohler was just trying to sell more engines.  And, considering my Briggs and Onans have not needed rebuilding, and every one of my Kohlers has needed rebuilding, I think their strategy worked.  LOL

[Tractorhead 9,212]

I agree with the issue, that a splash and Air cooling Engine needs „a higher rpm“ to last long,

but i normally never driven them at highest rpm, even i don‘t like that sound.

I didn‘t remember to read this in any Manual to run the engine only in Max. Rpm,

but i didn‘t know each Manual of each Machine, that‘s true.

 

One of my oldest mower has a Briggs & Stratton Original Engine, this works now over 16 years without any Troubles.

It runs on max. 3/4 throttle as long as i have it, before it was owned by my uncle, who‘s doing the same.

I used all my small Engines on 2/3 til max. 3/4 Throttle.

Correct Oilservice intervals mandatory.

 

The only Engine issue i had in the past 15 years was with my old Onan,

but about it‘s history nobody can tell what was the real reason for it‘s blasted cylinderhead.

It was in a burnt barn, harmt by fire distinguisher and after that nearly a half year outside stored without cleaning

and more other non ideal topics.

But on closer inspection, there was no signs of Oil failures.

The Piston looked used, but it was good in shape.

[JCM 10,225]

I wish I could offer some guidance on your carb question but I can't, what I can say about engine RPM is that I have owned my 312-8 since 1989 when I purchased it new and I can honestly count on one hand how many times I have run that 12 HP Magnum at full throttle,that being said I have always used the same brand oil, kept the engine chaff screen and air filter and pre cleaner fresh and kept the cooling fins clean with the air compressor,hope I didn't jinx myself. 3/4 throttle seems best.

[Stepney 2,354]

Eric, our two 'sister kohlers' are both 16's, and I have an early Carter off a 8hp Clinton on mine at the moment. Runs just as good as can be, granted, coincidentally I'm using the sickle bar, so I'm really never getting over half throttle. If anything I'd say low speed performance is improved, due to the smaller venturi. I've had 3 16hp Kohlers, and for some reason those are the only Carter carbs I have ever had issues with. I forget the size number off the top of my head. 

 

As to the operating rpm.. Kohler had these all over the book. My Kohler powered Winco generator is a full-speed 1800rpm unit. I had an old trash pump govorned at 2500. That was a Kohler 10. Works just fine. Running great after 50 years. Most of my tractors, even after an overhaul, I cut the max speed back to say 3200 instead of 34-3600rpm. Sure my 1952 REO single left the factory at 4000rpm governed speed, and still holds it .. but to me thats fast for such a old engine. 

[wh500special 2,272]

I’ve convinced myself that the need for full speed operation has nothing to do with cooling.  The airflow over and heat generated by the engine are linearly proportional to engine speed, so we should expect that cooling would be adequate at lower engine speeds.  

 

This is evidenced by the 1800 rpm generator mentioned above. 

 

Similarly, I can’t believe it would have anything to do with the splash lubrication system.  I’m sure there’s a lower bound to how hard a dipper has to hit the pool of oil in the sump to cause a decent splash, but even at idle speed that thing is really moving.   Besides, if they didn’t oil at idle, you’d expect the manufacturers not to provide any kind of throttle control setting between stop and wide open throttle.  

 

Pressure lube engines could be different I suppose if they use hydrostatic bearings on their rotating shafts.   I would think the oil pumps would keep the fluid film alive in there under low speed/moderate load but I don’t know.  

 

I would expect the high speed requirement has more to do with not wanting to lug the engine.   One of the primary tenets of engineering is the ability to size things properly to the task, so I would expert that engine power selection was usually matched to the work capacity of the machine to which it was mated.   The only way to get all the horsepower required for near full load tasks would be to run the engine at its rated speed so that it is making rated power.  

 

But if you’re pulling a cart with your gear drive tractor, you can probably throttle back to as low as you want to go since it doesn’t take that much power.   Within reason of course.  

 

On a hydrostatic tractor there are other issues requiring the engine to be run at high speed.  Power transmitted to the ground by the transmission is proportional to the product of pressure and flow rate in the hydraulic loop.  For any given load, if you reduce engine speed you also reduce flow rate by the pump and therefore require pressure to rise to archive the same output power.  

 

Higher pressures are harder to handle, bypass more, shear the oil more greatly,  etc.  And they can build up more heat. So even for short little jaunts with a loaded hydro, it’s probably best to run at nearly the rated

engine speed. 

 

I’m not a mechanic, but I would expect your 12 hp carb to run just fine on your larger engine.  The air/fuel mix will remain true.   But since you’ll be limited by the amount of air and fuel you can pump through the thing you will just expect the engine to wheeze under higher loads.   I would think that under no load or light load you would still be able to hit the rated rpm, but load it down and you’ll find the upper bound of what that carb can do. 

 

I’ve noticed that even under a mowing load there is still some room left for the governor to add more throttle to get through a tough spot.  So I would infer that even that 16 hp carb on a k341 running under a 48” deck load is

still not kicking out all 16 horses.   

 

You guys might remember that Dale G from Michigan years ago fabricated a 76” deck for his c160 and reported that even then he still had governor left in all but the toughest mowing.  

 

So who knows, maybe that 12 hp carb will do almost everything you need. 

 

Steve

[Stepney 2,354]

10 minutes ago, wh500special said:

 

This is evidenced by the 1800 rpm generator mentioned above. 

 

Similarly, I can’t believe it would have anything to do with the splash lubrication system.  I’m sure there’s a lower bound to how hard a dipper has to hit the pool of oil in the sump to cause a decent splash, but even at idle speed that thing is really moving.   Besides, if they didn’t oil at idle, you’d expect the manufacturers not to provide any kind of throttle control setting between stop and wide open throttle.  

 

Pressure lube engines could be different I suppose if they use hydrostatic bearings on their rotating shafts.   I would think the oil pumps would keep the fluid film alive in there under low speed/moderate load but I don’t know.  

 

On this subject, I have 3 engines here in semi occasional use all well into their eighties. Old splash lube farm engines. They loafed away at 3-400rpm for all their lives and haven't cooked a bearing yet. Work on the same principle as our engines now. Just oil dippers on the rod. I have one old Briggs and Stratton with a glass side plate on it, used for oil demonstrations funny enough. It's incredible just how much that thing tosses at full speed. But even a very low idle is more than adequate. Of course, you would never want to load an engine at such speed. But 1800rpm is more then fine in my book. For many years I idled around on a JD 116 with the boxer briggs engine. An engine famous for exploding due to 'oil starvation' at low speeds. Seen many come apart running at full tilt all their lives .. my 116 is still happily chugging along sucking leaves 20 years later. I'm no engineer .. but that's my take. Briggs also furnished engines to Winco. Also in the 1800rpm form. No different then a standard model 23 from the 50's era, with a more sensitive governor. Just like the Kohlers. I usually won't work them hard any lower then 1800 however. 

[ZXT 2,401]

I would imagine it would be fine at lower RPM, but at higher RPM HP and TQ will suffer. I never have run engines at full RPM for any length of time, and see no reason to do so. As has been mentioned, they sling oil plenty fine at lower RPM, and the increased RPM increases heat considerably. I usually run about 3/4 throttle when mowing. 

 

Since the Chinese replacement carbs aren't but about $12, I don't see the reason to waste a good 10-12 HP carb on a 16. 

[ebinmaine 72,719]

I ordered the correct Kohler carb from Lincoln @A-Z Tractor

 

Tried the Chinese route. Done with that.

I don't mind fixing tractors but I need a little more dependability. I've messed with this carb enough already.

 

I rarely if ever run over 3/4 throttle but do pull VERY heavy loads so I decided to go with the oe.

 

[Sarge 3,465]

To be able to hit the full torque output of a Kohler, which is what they are so good at producing means it needs that bigger bore carburetor. Putting a smaller carb on it will allow it to run, but it cannot flow enough air to produce its full capability of horsepower and torque. That 16hp engine, for no bigger than it is can process a lot of air volume - look at what little mods the pulling crowd is doing to those engines and once they open up the intake air path - that is when they can achieve the bigger power numbers.

 

Sarge