# 3,600 rpm std for all 4 cycle, is it a safe rpm



## JLawrence08648 (Jan 15, 2017)

Is the 3,600 rpm maximum setting rpm the same for all 4 cycle engines, lawn and snow, Tecumseh, B&S, Honda, Kawasaki, Kohler, Wisconsin Robin Subaru, Predator, Loncin, ......

Old and New engines?

Is 3,600 set in stone that it is what it should be and we should adjust to that number for expected and reasonable engine life or will there be much of an increase in engine longevity if it was lowered to 3,500, 3,400?

If raised to 3,700, would this shorten the engine life substantially, substantially increase the chance of engine failure?

The above is general to all 4 cycle engines.

Now specific to snowblowers since for many who are not in the heavy snow belt states of 3x/week, the snowblowers are not being run as long or as often as a lawn mower is, snowblower rpm recommended on this forum is 3,600. Are we pushing the chance of failure by raising to 3,700? or higher? There's a performance improvement when the engine rpms is raised from 3,000-3,400 to 3,600, will we see much of a performance improvement raising it to 3,700 or 3,800? Especially if it's worth the chance of engine failure or substantially shortening the life of the engine


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## UNDERTAKER (Dec 30, 2013)

JLawrence08648 said:


> Is the 3,600 rpm maximum setting rpm the same for all 4 cycle engines, lawn and snow, Tecumseh, B&S, Honda, Kawasaki, Kohler, Wisconsin Robin Subaru, Predator, Loncin, ......
> 
> Old and New engines?
> 
> ...


*Always consult your local friendly hood service manual on proper engine RPM'S.k:k:k:k:k:*


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## 524SWE (Jan 20, 2017)

It does appear 3600 rpm has become the default for small engines, I certainly would check any manuals I could nonetheless.


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## RIT333 (Feb 6, 2014)

My Toro PowerMax 1028 specifies 3300 +-150 RPMs

It is a Tecumseh SnowKing, vintage 12 or so years old - maybe more.

Should I "overclock" it to 3600 RPMs ? I think I bought it up to 3450, bit wondering about anyone's opinion.


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## 524SWE (Jan 20, 2017)

RIT333 said:


> My Toro PowerMax 1028 specifies 3300 +-150 RPMs
> 
> It is a Tecumseh SnowKing, vintage 12 or so years old - maybe more.
> 
> Should I "overclock" it to 3600 RPMs ? I think I bought it up to 3450, bit wondering about anyone's opinion.


I don't think you'd gain much by raising it another 150 rpms especially since it's a flat head engine.


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## cpchriste (Jan 19, 2014)

Yes, most are 3600. +1 a few more revs aren't worth the risk.
Memory tells me the Hondas and Yamahas are more like 4000rpm.
Never try to overspeed a 8HP Tecumseh.
People have posted here that the predators can and will run overspeed reliably.


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## RIT333 (Feb 6, 2014)

Agreed - was just looking for someone else's opinion that would match mine. Besides, I am throwing plenty far enough already. If I throw any further, I will be breaking neighbor's windows. I probably will add an impeller kit, just for the slush, Right now, my gap is pretty narrow - probably about 3/8" so I won't gain much distance, but hopefully will be able to throw slush. Seems like, with "global warming" in the Adirondacks, we are seeing more slush then ever, and with the Donald, it will only get worse. Or better - depending on which side to the temperature fence you are sitting on !


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## justintendo (Jan 2, 2017)

the lct ax208 that came with my ariens path-pro runs 3650 or so out of the box..im not sure if it turns the same speed in the two stage ariens that use this motor.
its a different animal..but my lawnmower uses a honda gcv190 engine, and it was super slow from the factory. turned 2500 out of the box. i saw the same engine used in pressure washers and such turned over 3k..i ended up adjusting the mower to run 3400 and it mows awesome now, and fills the bag much better. it does use more fuel than before and is louder, so im sure thats what the manufacturers are striving for. i still have enough fuel to do my property from a full tank so im happy with it. i did just check my valve clearances this winter on it after 3 seasons of mowing and they were very close to being dead on.
definitely pays to know what rpm your equipment turns and make adjustments or experiments if needed.


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## GustoGuy (Nov 19, 2012)

524SWE said:


> I don't think you'd gain much by raising it another 150 rpms especially since it's a flat head engine.


 



Agreed. You only risk engine failure over 3600 rpms on a Tecumseh flat head. Honda engines and the clone engines often run stock at 3800rpms and connecting rods in torture tests have shown them hitting 5500 rpms and going into valve float without breaking. Clone engine flywheels are considered unsafe at rpms exceeding 4000 and can break apart and injure you. So get a billet rod and flywheel and new valve springs if you are going to race these engines.


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## GoBlowSnow (Sep 4, 2015)

I wouldn't go over 3600. I run 3500-3550.


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## GregNL (Jan 9, 2017)

3800-4000 rpm is the recommended engine speed on my Yamaha, I run it at 3920. I would assume most other Yamaha's and Honda's are within that range.

Will I extend the life of the engine by reducing the speed to 3600 rpm? Maybe, I'll never know as the engine may go on for another 10+ years and suddenly fail while operating at the current factory recommended speed. Before I purchased an RPM Meter I had it running at close to 4500 rpm for a few minutes, did that thing ever move snow, I wish I could have kept it there but I wasn't risking putting it on the edge of redline as obtaining parts to rebuild a 25 year old engine are no longer available.

Be it an engine in a vehicle, plane or ship, maintenance intervals are done based on distance or time. Anything could happen during that period whether you run it slow continuously or fast though the higher stress levels exerted are definitely a cause of failure, I've seen it first hand on ship with massive turbos imploding or various other problems. That being said, keep your machine set based on the recommended speed to ensure optimum performance and longevity. If and when it blows up get a new one, for $99 for a repower in the US or ~$300 in Canada, I wouldn't concern myself with the life of a snowblower engine too much by under-revving it.


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## Spectrum (Jan 6, 2013)

First off there is engine max and application specific max RPM. Engines of a given TYPE to use the B&S term will be set to a specific no load high speed. There used to be a blue engine sales binder that had those numbers. I have been going back and forth with B&S on this and they keep going back to their service manuals. The B&S manual in front of me instructs set-ups as high as 4000 RPM.

Lower speeds are often the result of equipment constraints. For instance walk behind mowers have a blade tip limit. Longer blade, bigger radius, slower engine. Other times a certain point in the torque curve is desired. RPM may be set to limit force by virtue of velocity.

3600 RPM is the common safe number but the more I dig the less I'd use the term "set in stone". At 3600 you are in very comfortable territory.

Pete


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## classiccat (Mar 1, 2014)

Spectrum said:


> First off there is engine max and application specific max RPM. Engines of a given TYPE to use the B&S term will be set to a specific no load high speed. There used to be a blue engine sales binder that had those numbers. I have been going back and forth with B&S on this and they keep going back to their service manuals. The B&S manual in front of me instructs set-ups as high as 4000 RPM.


Comfort knowing that I'm not the only one scratching my head on this one. I don't have the stones to push my 170402 ('70 7hp) to 4k...guess that 3600 RPM hum is burned in my brain as well.


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## UNDERTAKER (Dec 30, 2013)

524SWE said:


> I don't think you'd gain much by raising it another 150 rpms especially since it's a flat head engine.


*I think those are OHV engines.:emoticon-south-park*


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## ourkid2000 (Feb 27, 2017)

I always set mine to 3400.


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## Spectrum (Jan 6, 2013)

AH HA! I finally found it. In this case we're looking at the 8 HP B&S L head engines. If you go to this link to will see that FACTORY ENGINE SETTINGS often exceeded 3600 RPM. It so happens that for the Gilson I'm interested in tonight the governor was set for 3500 RPM.

A Google search for "briggs engine sales manual" yields others.

Pete


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## 1132le (Feb 23, 2017)

I set the tecumseh 13hp ohv 358 cc @ 3750 as per the no load spec
The motor is rated @ [email protected]


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## 43128 (Feb 14, 2014)

i run my predator 212cc on my 910018 at 4400 rpms and have not had a single problem. tecumsehs cant go anything over 3600 rpms without risking throwing the rod


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## RedOctobyr (Mar 2, 2014)

4400? That's pretty cool  I've read a bit about hopping up the 212cc, I think it was, I believe there were even dyno plots. Even if the torque dropped off above 3600, you'd still throw the light snow further, before the RPMs sagged back down towards 3600. 

I have a Tecumseh OHSK10, OHV. It would be cool if it could handle >3600, but I don't want to push my luck and possibly blow the engine.


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## 43128 (Feb 14, 2014)

RedOctobyr said:


> 4400? That's pretty cool  I've read a bit about hopping up the 212cc, I think it was, I believe there were even dyno plots. Even if the torque dropped off above 3600, you'd still throw the light snow further, before the RPMs sagged back down towards 3600.


i bought it from a small engine repair place in manchester ct along with a gx200 from a pressure washer, 20 bucks each. the honda fired right up the predator needed a new carburetor. it had many hours on it when i bought it and since i only had 30 bucks into it i figured i would mod it a bit and see what it could do. so far its been holding up great, but i would never do those mods for a customers engine. i have been amazed with its durability


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## 1132le (Feb 23, 2017)

Does anyone know if the tecumseh ohv engines blow connecting rods like the L heads do?
I think iam going to lower the8 hp L head to 3600 from 3700 and the 13hp ohv to 3675 from 3750


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## 43128 (Feb 14, 2014)

1132le said:


> Does anyone know if the tecumseh ohv engines blow connecting rods like the L heads do?
> I think iam going to lower the8 hp L head to 3600 from 3700 and the 13hp ohv to 3675 from 3750


i wouldnt go over 3600 with any tecumseh personally


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## RIT333 (Feb 6, 2014)

43128 said:


> i would go over 3600 with any tecumseh personally


Would or Would not ?


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## RedOctobyr (Mar 2, 2014)

It's only a guess on my part. 

But there seems nothing inherent to an OHV engine design that would make the connecting rod less likely to blow. 

So I'd probably err on the safe side, and assume the OHV Tecumsehs would still be prone to blowing if revved too high. But if there's evidence to the contrary, I'd love to hear it.


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## 1132le (Feb 23, 2017)

RedOctobyr said:


> It's only a guess on my part.
> 
> But there seems nothing inherent to an OHV engine design that would make the connecting rod less likely to blow.
> 
> So I'd probably err on the safe side, and assume the OHV Tecumsehs would still be prone to blowing if revved too high. But if there's evidence to the contrary, I'd love to hear it.


That sticker is why i set it to 3750 its right on the blower same engine mine has thats a pro mine is not
Some engines have design flaws in them the the ohv being newer and not china built you would also think tecumseh would have changed any flaws in the con rod area it knew about iam sure they tested motors
I bet most L heads that blew up were low on oil or had dirty oil or reved higher then 3750 but nobody knows
Also i found some power curves last night for brigs and tecumseh motors playing with the calculator using torq x rpm div by 5252 was only adding .6 or so hp running it all the way up so its not worth it
Ill lower them some today


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## RedOctobyr (Mar 2, 2014)

Cool. Mine is older, it doesn't have that info on the sticker. 

The Ariens service manual for mine says 3500 +/-150 for the OHSK100-130. And 3600 +/-150 for the HMSK100 and OHM90. 

As I recall, I set my OHSK100 to the high limit, 3650.


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## FearlessFront (Aug 18, 2016)

My non hemi Predator (Chonqing rato) is rated at 3800 rpm. The hemi version (Loncin) is rated at 3600 rpm, I noticed on the box. I run my non hemi Predator 212cc at 4500 rpm, all the time, constant for the last 3 years, no issues. I have seen older Briggs L-Heads rated at 3800 rpm and said so on the front shroud label. Most Tecumseh engines were rated at 3600 rpm, however, people who use those engines on mini bikes often run them well above 3600 rpm. I had a 1969 Tecumseh H50 that ran stock up to 4300 rpm. So no I would not say 3600 rpm is the standard, out least not anymore and in my opinion, the non hemi predator is better than the hemi, its rated 200 rpm higher and runs to 4500 rpm max, no issues. It used to be most engines were not supposed to be run above 3600 rpm and horsepower was rated at 3600 rpm, yet the engines often ran closer to 3300 rpm and Torque is often derived at, at 3300 rpm, but engines are not rated in hp any longer, so the 3600 rpm has basically gone out the window. No it's not standard every engine and engine manufacturer is different. Many engine's including Tecumseh will usually throw a rod or burn up above 3600 rpm, but now with these OHV engine's, their running at higher rpm. Also your 2 cycle engines run at much higher rpm's than a 4 cycle. A small 4 cycle engine can be ran and rated anywhere between 3300 rpm and 4500 rpm I've seen. The older L heads were all mostly rated and ran at or below 3600 rpm. Things have changed.


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## FearlessFront (Aug 18, 2016)

43128 said:


> i run my predator 212cc on my 910018 at 4400 rpms and have not had a single problem. tecumsehs cant go anything over 3600 rpms without risking throwing the rod


Same here I run my non hemi Predator right around 4400-4500 rpm stock, no issues and it definitely makes the engine run more powerful than the 6.5hp its rated at. At 4400-4500 rpm those engines are actually putting out around 10hp. Tecumseh L- heads were not recommended to go over 3600 rpm, unless you have a high performance engine with the high performance governor, than people run them up around 4300 rpm plus but not constantly like the predator. Also like one guy said the Predator engine is louder than my Briggs well yes its louder when running at 4500 rpm, which the Briggs engines are not running at, but when you bring the Predator down to 3600-3800 rpm its the same volume as a Briggs, but these engines are capable of 4500 rpm and even if it blows in 10 year's another $99 will buy another one. They turn the machines they are on into beasts.


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## YSHSfan (Jun 25, 2014)

Generally, yes 3600rpm is the most common speed, but I would go by the service manual spec. Yamaha 8hp engines run at 3800rpm and Yamaha 6hp engines run at 4000rpm, both flat head engines.


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## Sign216 (Feb 14, 2017)

1132le said:


> i found some power curves last night for brigs and tecumseh motors


Can you post the curves, or the links to the site. 

I'd like to see the what my Tecumseh L head is doing at different rpms.


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## tpenfield (Feb 24, 2015)

Just catching up on this thread a bit . . .

It seems that many of the work engines are 'rated' to go up to 3600 RPM. Here is a power curve that I found for my new Briggs 305cc (14.50 GT) engine.









The torque curve is pretty flat and the engine is spec'd at 3600 RPM max. . . So, the maximum HP ( 9.596 hp) is also at the max RPM.

I would imagine that many of the engines we use in our blowers and yard equipment are pretty similar in terms of their power curve characteristics.

BTW - I would love to run my Predator 212cc at 3800-4000 RPM, just a bit afraid though . . .


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## Sign216 (Feb 14, 2017)

tpenfield said:


> Just catching up on this thread a bit . . .
> 
> It seems that many of the work engines are 'rated' to go up to 3600 RPM. Here is a power curve that I found for my new Briggs 305cc (14.50 GT) engine.
> 
> ...



So here's a question. Torque maxes at 2,900 rpm, and hp at 3,600. 
For optimum performance, which do you choose?


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## tpenfield (Feb 24, 2015)

If I were me, I would set the throttle at WOT (3600) and let the machine do its thing. As the load increases the RPM will drop towards the 2900 RPM level where it has the most torque. If the machine can hold it there, then fine. If not, then you have to back off a bit to what the machine/engine can handle.


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## 1132le (Feb 23, 2017)

Sign216 said:


> So here's a question. Torque maxes at 2,900 rpm, and hp at 3,600.
> For optimum performance, which do you choose?


At 2900 rpm you have 8 hp at 3600 you have 9.59 hp


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## RedOctobyr (Mar 2, 2014)

tpenfield said:


> If I were me, I would set the throttle at WOT (3600) and let the machine do its thing. As the load increases the RPM will drop towards the 2900 RPM level where it has the most torque. If the machine can hold it there, then fine. If not, then you have to back off a bit to what the machine/engine can handle.


Exactly this. If you run at 3600, and the load is such that the engine can't hold the RPMs, you'll drop into the more-torque RPMs anyhow, closer to 2900. Which will help prevent the RPMs from sagging further, and worst-case, you'll simply end up at that 2900 anyhow. In the meantime, you get further throwing distances, etc. 

But set it to 2900, and you won't throw as far, make less power, and will start to drop into a less-torque RPM range as soon as the engine speed starts to sag.


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## tpenfield (Feb 24, 2015)

Without an eye-glossing discussion of power and speed . . . with these types of engines performing the work that they are intended to do, you want to run them at the WOT throttle setting so the engine can give you what is has got. The load, the gearing, etc. at any given moment will decide how the engine responds.

Only if the gearing (belt ratio) is set to a high ratio, will the engine actually be able to reach its spec maximum RPM while under load. Typical gearing of these machines will cause the RPM's to drop off while under load to a point where the torque on the engine can hold it. . . at that point the HP output is less because the 'Torque x RPM' result is less.

Beyond that it is complicated . . .

FWIW - I have a 24" blower that 'had' a 5.5 HP engine and now has a 9.6 HP engine. My expectations (which I am soon to find out when I snowblow this storm) is that the nearly 2X HP engine will be able to run closer to its max spec 3600 RPM, because it has a lot more torque.


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