# Run full Throttle?



## dualTrace (Dec 6, 2015)

Hey guys.... My uncle who is the family mechanical guru, well deserved I might add, told me that it's necessary to run small air cooled engines at full throttle all the time or otherwise they might overheat. The thinking being that at lower speeds there is insufficient airflow over the cooling fins to keep things cool. Not sure I go along with that, what are your thoughts on it?
charlie


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## micah68kj (Oct 8, 2011)

Listen to your Uncle. Why are there so many small, air cooled engine w/o throttle controls? You start them up, give them a few seconds then open them up.


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## Spectrum (Jan 6, 2013)

Logical operation of the implements usually takes over. Mowers, blowers and such simply need RPM to perform so it's usually idle or all.

I have never heard that position on engine cooling but I have to believe that there is some truth to it. It probably comes down to shades of gray including HP, RPM, load (governor pull) and even block & fin cleanliness.

Pete


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## ELaw (Feb 4, 2015)

I don't buy it!

Most engines that have no throttle (ie run full speed all the time) have other variants that do have throttles. If running them at slow speed could cause damage, they would never have a throttle.

In one way your uncle's argument does have a sensible basis in physics. With most blowers like the ones that cool small engines, airflow doesn't increase linearly with speed... it increases exponentially. So yes at higher speed there's more cooling.

But "the rest of the story" is this: at low speed, the engine is generally under very little load. Idling at 1200 RPM or so, the engine is only producing a tiny fraction of the amount of heat it produces at 3600 RPM and full load.

Now putting a heavy load on an engine at low RPM could tip that balance... I definitely would not advocate running your snowblower through a foot of heavy snow with the engine spinning at 1500 RPM. But the usual mode of operation where the engine is idled when not actively being used, and at high RPM when under load, should be fine.

I also happen to be of the opinion that starting an engine at full throtle is very unkind to it. Expecting it to produce a lot of power, even momentarily to come up to governed RPM, before the oil has a chance to circulate has to be tough on an engine. Whenever possible, I usually start engines with the throttle about 1/4 open so the governor can help keep it running but it stays at low RPM until the oil has had a chance to get everywhere it needs to be.


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## ctdave (Sep 11, 2015)

the fins for air cooled engines, either large or small, are to create a larger surface area to keep the engine cooler. ( the same principle with computer cpu's and memory) the movement of the equipment (or fan ) will help air move through the fins to aid in cooling. nothing to do with engine speed. the use of an air filter on small engines does help it run cooler and use less fuel, and are used on small engines mainly for warmer weather. most snowblower engines do not have an air cleaner to prevent water and ice build up in the carb, unless their is a heater of some type to prevent icing, such as on the older ariens where the engines were used for summer attachments. but the lack of an air cleaner makes these engines run hot and will be damaged if used in warm weather. however your uncle is correct also. when in "use" and at full throttle the equipment is in motion therefore more air movement across the fins (larger surface area ), keeping the engine cooler. when sitting and at idle the equipment is mostly not being used (in motion) therefore less air passing over the fins allowing the engine to run hotter than when at full throttle and in motion. it is very important to make sure the fins are clean and not clogged with debris. so bottom line it is not the engine speed, but the movement of air through the fins. and it cuts cost to the maker having no throttle. hope that make sense


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## jtclays (Sep 24, 2010)

Another aspect of full throttle running is on lawn tractors, particularly with hydro trans. Most are now set up to run by belt. The input pulley of the trans has a fan also that runs to cool the trans. The belt that drives the fan comes from the engine PTO, if you run low idle the perception is your "babying" the unit. In reality, operator weight and unit weight still has to be overcome by the engine and trans. Hot trans equals short life. The hood area on tractors is designed to funnel air over the engine at full throttle also.
On liquid cooled engines, it works against you a bit in the winter use. In the summer running at half throttle and idle is working against the design.


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## Kiss4aFrog (Nov 3, 2013)

If running at a mid speed would cause a problem it should show up more on summer use equipment. Seeing we're using blowers in 50-80 degree cooler weather we have a huge advantage in cooling to begin with. 

Not to say there isn't something to the idea but I've never run into a problem with my rider and when I 'm using it for moving stuff, dirt, brush, plants, ... I usually run at mid throttle to be easier on the engine and less noise for the neighbors, no problems noted yet.


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## jtclays (Sep 24, 2010)

K4frog, It's a debate that will never end. 25% of mytractor forum seems to be dedicated to arguments over the best way to run an engine. Full throttle wears the internals vs low throttle overheats the externals. I stay in the camp that a properly lubricated engine is designed to run at full throttle and a working hydro needs to be clear of debris and have a nice fan blowing on it. An overheated hydro can make a pristine tractor a parts machine, IMO.
Snowblowers and the temps we run in, likely not an issue, agreed.


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## micah68kj (Oct 8, 2011)

jtclays said:


> K$frog, It's a debate that will never end. 25% of mytractor forum seems to be dedicated to arguments over the best way to run an engine. Full throttle wears the internals vs low throttle overheats the externals. I stay in the camp that a properly lubricated engine is designed to run at full throttle and a working hydro needs to be clear of debris and have a nice fan blowing on it. An overheated hydro can make a pristine tractor a parts machine, IMO.
> Snowblowers and the temps we run in, likely not an issue, agreed.


^^ ^^ ^^
What jt said.


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## Shryp (Jan 1, 2011)

I have always heard that as well. I say go for full throttle. The other thing to remember is most small engines are splash lubricated so the faster you run them the more the oil splashes around.


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## Cardo111 (Feb 16, 2015)

I can only speak from my personal experience using OPE for many years and always keeping up on maintenance. I have never had a small engine overheat on me. I often run my engines at idle if they include a throttle control. Under load I run them at full throttle. I always have my throttle in the fast position when starting them as most owner's manual will specify. I will then lower the throttle until the machine will be used under load.


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## jrom (Jan 10, 2014)

^ +1 ^


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## ELaw (Feb 4, 2015)

Cardo111 said:


> I can only speak from my personal experience using OPE for many years and always keeping up on maintenance. I have never had a small engine overheat on me.


This actually brings up an interesting thought, as if you'd asked I would have said the same thing: "I've never had a small engine overheat".

But... if a snowblower (or whatever) engine overheated, how would you know?  It's not as if they have temperature gauges... or liquid coolant that would boil and make steam and thus be very obvious.

And actually... what constitutes overheating on one of these engines? With a liquid-cooled engine, overheating is a very clearly defined point... it's when the coolant boils. But of course that's not the case with an air-cooled engine.


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## nwcove (Mar 2, 2015)

ELaw said:


> This actually brings up an interesting thought, as if you'd asked I would have said the same thing: "I've never had a small engine overheat".
> 
> But... if a snowblower (or whatever) engine overheated, how would you know?  It's not as if they have temperature gauges... or liquid coolant that would boil and make steam and thus be very obvious.
> 
> And actually... what constitutes overheating on one of these engines? With a liquid-cooled engine, overheating is a very clearly defined point... it's when the coolant boils. But of course that's not the case with an air-cooled engine.


how would you know ? you may get a whiff of an odd smell of burnt oil, then you may notice the engine is loosing power, then you may notice the engine has stalled, and you cant pull the cord.....engine is cooked. jmo


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## bwright1818 (Dec 2, 2014)

I'm not about to get sucked into this vortex but I have never seen a four stroke, air cooled engine throw a rod at anything BUT WOT......Now, I know what's going to be said: "The wear occurs at lower speed and just fails at WOT." Maybe....


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## nt40lanman (Dec 31, 2012)

Especially on a snowthrower, I can't imagine an overheating problem. I like to work mine hard to melt the ice off the shroud.


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## ST1100A (Feb 7, 2015)

The main reason is because of the way they are carbureted. If you don't run them at full governed speed, you risk "loading" them up with carbon in the cylinders. 
Most small engines don't atomize the fuel that well at lower running speeds, causing larger fuel droplets that don't burn as well or cleanly at low speeds. At higher speeds they atomize the fuel into smaller droplets, therefore cleaner burn and better power.
The cooling effect is nonsense, at a lower speed the engine will run cooler by producing less heat, as a higher speed will run hotter, thus the higher fan speed to cool it.
The way the engines carburete themselves at lower speeds are generally too rich. Small engine carbs aren't designed as high tech as automotive carbs or fuel injection is to keep the cost down.
More expensive fuel injected engines don't have as much problems running at lower speeds as carbureted engines do, they are also more expensive to manufacture.


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## CarlB (Jan 2, 2011)

I have also never had a 4 stroke air cooled engine overheat even in 90+ degree temps when at any engine speed. That being said i don't run my engines less than fuel throttle when they are having to do any real work. The only exception is my 26" cub cadet snow blower with the 11hp engine and larger impeller pulley and impeller kit. I find that i only need to run it at 1/2 throttle or less in normal type snow if the snow is less than 8". It still will throw snow plenty far and uses much much less gasoline and is very quiet.


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## pfn (Dec 24, 2010)

Does anyone know what a properly tuned engine's cylinder head temp should be? Just curious as I have a few cht gauges around from my karting days and may install them my snow blower and leaf blower.


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## nt40lanman (Dec 31, 2012)

CarlB said:


> The only exception is my 26" cub cadet snow blower with the 11hp engine and larger impeller pulley and impeller kit. I find that i only need to run it at 1/2 throttle or less in normal type snow if the snow is less than 8". It still will throw snow plenty far and uses much much less gasoline and is very quiet.



YESSS!!! I live the sound too!!! Blasting out the snow but the engine has a lower tone and hum, and the impeller makes a noise like a wood chipper.

I overheated an air-cooled once, it was my mower and I was working it brutally. It started blowing oil smoke so I shut it down and let it cool, changed the oil on it and took it easy. It's been fine for years after but I go fairly easy on it.


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## Sid (Jan 31, 2014)

I run my 26' Sears/Murray at 3/4 throttle just as a concession to it's age. Never even had the head off, it will be 50 next year.
Sid


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## 94EG8 (Feb 13, 2014)

dualTrace said:


> Hey guys.... My uncle who is the family mechanical guru, well deserved I might add, told me that it's necessary to run small air cooled engines at full throttle all the time or otherwise they might overheat. The thinking being that at lower speeds there is insufficient airflow over the cooling fins to keep things cool. Not sure I go along with that, what are your thoughts on it?
> charlie


You shouldn't idle it for extended periods for that reason. You should be running at WOT when using the machine but not so much for cooling as for carbon buildup. People think they're babying something running it at half or 3/4 throttle and all that's happening is a lot of carbon buildup. 



Kiss4aFrog said:


> Not to say there isn't something to the idea but I've never run into a problem with my rider and when I 'm using it for moving stuff, dirt, brush, plants, ... I usually run at mid throttle to be easier on the engine and less noise for the neighbors, no problems noted yet.


You're being harder on the engine by doing that. You're getting excessive carbon buildup.


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## mammamoonbeam (Jan 6, 2018)

Does running full throttle make my Toro snow blower move faster across the ground? I would like to slow it down a little.


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## RedOctobyr (Mar 2, 2014)

Welcome to the forum! 

Almost certainly, yes. What model machine is it? 

Regardless of the machine's details, turning the engine faster will speed up the transmission, as well as the augers/paddles for the snow. Either of which would make it want to move faster. For a 2-stage machine, the transmission is what drives it. And for a smaller, single-stage machine, the paddles pulling against the ground is typically what drives it forward. 

But, depending on the model #, there is a decent chance that you can adjust the transmission to slow down your forward speeds somewhat. If you can post a little more details of what you have, people can help. 

On the original subject, I was using the lower-RPM approach yesterday for getting rid of driveway drifts fairly early in the morning. I slowed it from 3600 to 2900 RPM, it was *much* quieter, and still threw plenty far. I clear at full-throttle 98% of the time, it is nice to have the option of slower/quieter speeds, but I don't do it often. 

Having a tach/hour meter on the machine, at least I can see what I'm running at. 2900-3000 isn't that much slower than 3600 (it's not like I was at idle, around 2000), so hopefully it's not too bad in terms of cooling, carbon building, etc.


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## stromr (Jul 20, 2016)

WOT! Better cooling, better oil splash lubrication, better fuel atomization, longer engine life. Old flatheads or new OHV engines, never had a problem!


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## Clutch Cargo (Dec 27, 2015)

Uncle knows best.


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## 1132le (Feb 23, 2017)

Full throttle
They can debate it all the want its ok for them to be wrong i have a couple of small engines35 yrs old they still run
plus 1 on the splash oil
common sense says full throttle
maybe on a summer engine 10 hrs straight when its a 100 out but still cant see it the conditions are the conditions
if you are going to run it hard or tuff conditions it should be liquid cooled
winter is full throttle


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## Mike C. (Jan 28, 2016)

Yes-always-full throttle on a snowblower.The blower itself is designed to perform best at full throttle.

My father has some kind of thing about small engines running at top governor speed-he thinks it just abusing the engine.I can't convince him that small engines are designed to run at their top governed speed-for many years.Proper maintenance is the key to longevity.

I have his old Allis Chalmers Sno-Pro and hated the thing the first time I used it.It wouldn't throw dry snow more than 15 feet at best.One day I checked the engine RPMs at full throttle and noticed it was running under 3000.I set it factory spec and the blower became a different machine entirely.A few hundred RPMs makes a huge difference in performance.

I later discovered that he set the governors back on his other two blowers,as well.He claims there's no need to run those engines that hard and there's no changing his mind.


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## ELaw (Feb 4, 2015)

If he doesn't believe you, maybe he'll believe a company that manufactures snowblowers?

From the "operation" section of the manual for my Ariens ST824, under the "operation" subheading:

"5. Move Throttle to 'FAST' position."​


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## DriverRider (Nov 20, 2016)

Mike C. said:


> Yes-always-full throttle on a snowblower.The blower itself is designed to perform best at full throttle.
> I have his old Allis Chalmers Sno-Pro and hated the thing the first time I used it.It wouldn't throw dry snow more than 15 feet at best.One day I checked the engine RPMs at full throttle and noticed it was running under 3000.I set it factory spec and the blower became a different machine entirely.A few hundred RPMs makes a huge difference in performance.


So you took his very old babied machine and cranked the RPM up because it didn't throw snow the furthest on the block?:icon-rolleyes:
You have to think why some guys machines are still around and others are in the scrap yard.


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## ELaw (Feb 4, 2015)

My ST824's been clearing snow every New England winter since it was bought in about 1988, at full throttle, with no issues. It still has good compression, starts on the first pull, and makes power like it was new.


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## Mike C. (Jan 28, 2016)

DriverRider said:


> So you took his very old babied machine and cranked the RPM up because it didn't throw snow the furthest on the block?:icon-rolleyes:
> You have to think why some guys machines are still around and others are in the scrap yard.


Evidently you didn't read my post too thoroughly .I set the engine RPMs to FACTORY spec as according to the Allis service manual and the Tecumseh service manual.

The reason for doing this was because the thing couldn't throw snow for crap.This is why my father stopped using it.I couldn't convince him it was because of the low RPM.It was given to him, and believe me, the previous owner NEVER babied it.

These engines are made to run at full FACTORY SPEC. maximum RPMs-it doesn't hurt them.Relax,DR.


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## Mike C. (Jan 28, 2016)

ELaw said:


> My ST824's been clearing snow every New England winter since it was bought in about 1988, at full throttle, with no issues. It still has good compression, starts on the first pull, and makes power like it was new.


Same here,have two them made in the 1980's.Been run wide open since new,as they were meant to be.


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## SimplicityAlan (Jan 7, 2014)

Fresh Predator Hemi 212 repower. Mobil 1 5W30. 
Governed to 4200. 
I back off to 80% at times. Mostly running WOT and boy does it throw far.
Plan on a Stage 1 upgrade maybe next year. 
Header
Rejet with performance emulsion tube. 
Velocity stack for carb. 
They’ve been run 5200-5500 before valve float. 
Go big or go home!
I will be posting videos. 
I’m in it for the fun !!


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## jsup (Nov 19, 2017)

SimplicityAlan said:


> Fresh Predator Hemi 212 repower. Mobil 1 5W30.
> Governed to 4200.
> I back off to 80% at times. Mostly running WOT and boy does it throw far.
> Plan on a Stage 1 upgrade maybe next year.
> ...


Love it! I was wondering when the valves start to float on these. Do they make stiffer valve springs for these? Don't know how much faster you'd want to spin it, but I'd be interested to how fast it can go.


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## RedOctobyr (Mar 2, 2014)

Awesome, SimplicityAlan, I look forward to the videos! 

I think I've read that you can get stiffer springs for the 212ccs. And I remember reading about replacement flywheels, because there is a risk of the stock one blowing apart above some RPM, I forget what the threshold was. Pretty sure I saw mention of spinning these maybe above 7000 RPM, with upgrades? Very impressive. 

Again, I wish there was something that was this nice of an affordable starting point, for a little over 300ccs. Why not start with a little more oomph right out of the gates, eh? "There's no replacement for displacement". And for a blower, unlike a racing application, we don't care if the engine is heavier, we just want the output.


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## jsup (Nov 19, 2017)

Here's the thing, these engines were specifically designed to run the way they run. Flat RPMs all the time. Running them at those RPMs is no problem. The cam, and everything else, is designed to run at 3600 or whatever the spec is for the given motor. So run it there. I did some consulting for a performance company, made heads and blocks, one of the businesses they were in were building big generator motors (big block chevys) that ran a flat 3600 RPMS all the time. They ran a long, long time without issue. That's not a lot of stress on the parts these days.


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## jsup (Nov 19, 2017)

RedOctobyr said:


> Awesome, SimplicityAlan, I look forward to the videos!
> 
> I think I've read that you can get stiffer springs for the 212ccs. And I remember reading about replacement flywheels, because there is a risk of the stock one blowing apart above some RPM, I forget what the threshold was. Pretty sure I saw mention of spinning these maybe above 7000 RPM, with upgrades? Very impressive.
> 
> Again, I wish there was something that was this nice of an affordable starting point, for a little over 300ccs. Why not start with a little more oomph right out of the gates, eh? "There's no replacement for displacement". And for a blower, unlike a racing application, we don't care if the engine is heavier, we just want the output.


I haven't taken one apart, what kind of lifters do they have? I'm assuming solid. 

Here's a picture of the head I found, it's like they have shaft rockers, impressive.


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## SimplicityAlan (Jan 7, 2014)

On the valve float , I’m going by the go kart / mini bike forums. I plan on buying one more Simplicity Snowbuster to bring it to 3. I like the paddle style impellers. And I like interchangeable parts. Same belts. Same everything. The two I have are 5/24s. They share the same tractor as the 8/28. They’re from the 70s , overbuilt would be an understatement. 
Harbor Freight is right around the corner


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## SimplicityAlan (Jan 7, 2014)

Anyone else doing motor mods? I’ve got a double wide driveway , a big yard and 150’of frontage to throw my snow for distance!
Kinda like having a daily driver and something to play with on the weekends.


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## tpenfield (Feb 24, 2015)

Maybe at the next snow storm we could take out our IR temperature guns (or IR cameras) and run the engines at various speeds to check the temperature that they run while at those speeds 

I’m thinking at WOT the engine will be at its hottest.


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## DriverRider (Nov 20, 2016)

Temperature of the lubricating (cooling) oil would be a better barometer and I will guarantee you it will not be above the typical car oil temp of around 190-200 degrees F.


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