# Increasing RPMs to compensate for power loss from altitude, Why Not?



## dugt (Jan 23, 2020)

At 6000' my snowblower produces 18% less power, or so I've been told. Why not increase the RPMs 18% so that the power output is about that same as it would be at sea level? If the snowblowers RPM spec is 3,500 rpm, increasing 18% would be 4,130. I'm wondering why this isn't a common mod? 

Go Kart owners say the RPMs of our Honda snow blower engines can easily be increased to 6000 rpms. Higher rpms require stiffer valve springs. So, it seems Honda engines are ballanced and precision enough to handle much higher rpm's and since the increase in power is not beyond the typical power at sea level, it seems to me to have no disadvantages so why isn't it more common?


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## Oneacer (Jan 3, 2011)

I am only throwing in my 2 cents, but I would assume these engines were designed to run at a certain RPM, and increasing them by say 20% would put increased stress on the internal parts.

JMHO

BTW, what does your Snow Blower Manufacture say?


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## Town (Jan 31, 2015)

There are some threads/posts in the Honda Forum that suggests the Honda engine can be run to 4,000 rpm in stock form although the posters actually used 3,900 rpm as the max. The governor was set to a lower rpm (than 3,900 rpm) but the throttle had an additional setting to get the 3,900 rpm (extra power on demand manually). This is at sea level I think. Again the performance engine tuners were used to confirm the high rpm and the posters had 1332 machines with 3,500 rpm spec. So 4,130 rpm would be a stretch. And they were using larger main jets.

The other aspect is that engine power to engine speed is not a direct and linear relationship, so the 18% increase in rpm would not equate to an 18% increase in power. 

So if the 1332 Honda is lean at sea level it may be OK for the thinner air at 6,000 ft. It is possible that the dealer automatically swapped in the Honda recommended jet for 6,000 ft. In order to get more power it may be worthwhile seeing what main jet is installed in your machine and checking with Honda's recommendations for main jets at different heights above sea level. The Honda Forum may have some experience with your concern for more power and can advise.

Good luck.


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## orangputeh (Nov 24, 2016)

dugt said:


> At 6000' my snowblower produces 18% less power, or so I've been told. Why not increase the RPMs 18% so that the power output is about that same as it would be at sea level? If the snowblowers RPM spec is 3,500 rpm, increasing 18% would be 4,130. I'm wondering why this isn't a common mod?
> 
> Go Kart owners say the RPMs of our Honda snow blower engines can easily be increased to 6000 rpms. Higher rpms require stiffer valve springs. So, it seems Honda engines are ballanced and precision enough to handle much higher rpm's and since the increase in power is not beyond the typical power at sea level, it seems to me to have no disadvantages so why isn't it more common?


you may be playing with fire. i have lived in same area for 23 years and my old honda's do just fine as stock. i just make sure the rpms are up to spec. if you have the new HSS model you can re-jet carb. check re-jetting thread in Honda forum here.


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## dman2 (Sep 22, 2019)

I believe rpm is measured at the crankshaft. These small engines only have one cylinder, and you are making them run at 6000 rpm. That is like 24,000 rpm on cars. 3600 rpm is already a lot, unless it is a two cycles engine. They can't breath at higher rpm. Also, the connecting rod, valves springs and everything else can't handle that.

Go cart community is like street car community. They always push things to the limit and don't care much about reliability.
It costs a lot to modify anything, just so you know. They don't just simply increase the engine rpm. I did rather spend that money on a new bigger engine.

If you can just simply increase the engine rpm to get more HP, then every one else would do so. There will be no completions among engine markers. All engines rpm were set from factory at the safe limits. You can only play with it a little by adjusting the fuel jets and slightly increase the engine rpm.


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## dman2 (Sep 22, 2019)

Town said:


> The other aspect is that engine power to engine speed is not a direct and linear relationship, so the 18% increase in rpm would not equate to an 18% increase in power.
> 
> Good luck.


Yep, HP on those engines would be very likely to drop, or stay flat after 4000 rpm.


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## RedOctobyr (Mar 2, 2014)

Like they said. You likely won't see power increase linearly as you increase RPM, it depends on how the engine is breathing, etc. You would significantly increase the stress on the internals, which increases greater than linearly. 

And because you (presumably) aren't gearing down the engine's output, it may produce more power, but you're also putting a bigger load on it. It's now spinning the augers and impeller faster, for instance, which requires more power. So even if the power output went up, the demands on the engine are also increasing, unless you changed the pulleys and belts to maintain the stock RPMs for auger, impeller, etc. So it may not really be the net-benefit that you'd be hoping for. 

I would first make sure you have the proper jet for your altitude. Then, with a tachometer, set the engine RPM to the top of the governed RPM range spec. Or, if others have shown that your engine can safely handle 3900 but the spec is 3700 (I'm making up numbers), and you're comfortable with that, then set it to 3900. 

But it's more involved than just increasing RPM % by the amount of power you've lost. And the risk is blowing the engine if you increase it too far. 

Now, if you want to crank it up, but you have a spare larger engine ready to install if needed, that's different. Just ensure that you don't spin fast enough that you shatter the flywheel, or someone could really get hurt. For instance, the stock Predator 212cc engine flywheels are only considered safe to a certain RPM, then they risk coming apart if you go beyond that.


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## Shovel (Mar 26, 2019)

dugt said:


> At 6000' my snowblower produces 18% less power, or so I've been told. Why not increase the RPMs 18% so that the power output is about that same as it would be at sea level? If the snowblowers RPM spec is 3,500 rpm, increasing 18% would be 4,130. I'm wondering why this isn't a common mod?
> 
> Go Kart owners say the RPMs of our Honda snow blower engines can easily be increased to 6000 rpms. Higher rpms require stiffer valve springs. So, it seems Honda engines are ballanced and precision enough to handle much higher rpm's and since the increase in power is not beyond the typical power at sea level, it seems to me to have no disadvantages so why isn't it more common?


Chances are the engine will have a short life with 4130 RPM..the rods break on these things... Flywheels fly apart which is very very dangerous.
Depending on your engine you may actually have less HP at higher RPM s.
It just depends where your peak HP is..might be a little above the 3600 mark or even a little behind it...Some of the smaller engines tend to have a peak higher up though in the 4000 RPM range.
The engines are designed to have a peak torque in the 2400 to 2800 range ... this gives us a wide enough window to use our engine without a sudden power fall off.
Peak HP is just what's it's going to be..they don't care if it's 3600 or 4200 RPM.

Also doubling impeller RPM consumes 4 times as much power passing the same amount of snow....So any gain you may have is going to be offset some as well..unless you reduced your impeller speed.
The Honda and Loncin engines seem to handle the abuse of overspending well enough..But yet I wouldn't over due it..I am surprised Honda is going past the 3600 or 3750 mark.
None the less where 3900 RPM originates kinda goes back to mini bikes and the four wheel brothers...There wasn't a no load RPM per say as they had centrifugal clutches..the engine wouldn't see 3900 RPM as it was under a load..You could take off the chain and set no load to 3900..which put you back in the 3600 RPM range while topping out your speed with a person going straight and bent over to reduce drag.
For ages 3750 was considered the maximum allowed RPM with 3600 preferred..However a generator needs 3600 RPM ...so needs to have a higher no load RPM then get pulled back down to 3600..hence 3750
I would still consider 3750 to be the max I would want to go..and not play around beyond.. Yeah there is a small area above to play with..buts it's not much and life will be shortened... drastically if the rod breaks.
Also to consider...let's say you have top no load set to 3750 RPM...You are working the machine then let go of your handle to stop the impeller...the governor overshoots briefly on the correction speeding you past the 3750 mark..we touched that 3900 RPM mark for a brief moment just by unloading the engine.
Now let's start to run out of fuel or the carb clogs a bit and the engine hunts..It will be bumping that 3900 RPM quite a bit


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## Shovel (Mar 26, 2019)

As a side note... It's a Honda with a large engine and a fast impeller.. really isn't a need to mod as it should be great right out of the factory... Essentially 'pre modded'

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## dugt (Jan 23, 2020)

Thanks for the replies!

To clarify, the blower that I want to mod first is a 15 year old HS724. I bought it used and don't know what jet is in it but since it is pre-CARB, if it has the original jet, it might be a little rich for 6000'. I should check the jet size. 

Net Power Output (HP)	5.5 (4.1 kW) at 3,600 RPM
Net Torque (lbs./ft.)  9.1 (12.4 Nm) at 2,500 RPM
Max. RPM	3,600

I only use this blower on a 22'x11' deck that gets deep snow because snow blows off my high and exposed roof onto this deck. A bigger blower would be cumbersome turning on this small deck. (I have a new HSS1332ATD for my 80’x30’ driveway.)

I realize that increasing RPMs would increase wear caused by any imbalanced components in the engine. However, I read some posts in a Go Kart forum and they run Honda engines up to 8,000 rpms but 6k rpms is more common. Engine precision doesn’t seem to be a problem because these are well made engines. Predator engines are becoming more popular because they cost one third as much, $100 vs $300 for a Honda GX200. (These engines are cheap!) However Predators are known to break flywheels and rods. Honda’s are relatively tough at higher rpm’s. 

Some have mentioned diminishing returns of power at RPMs above spec, 3600 rpm in my case. Then why do Go Kart racers push them up to 6000 rpms with few if any mods other than adjusting the governor?

Aren’t Go Karts raced at elevations much closer to sea level? At sea level and at 6000 rpms they are making much more power than I’m trying to get from a blower at 4200 rpm’s and at 6000’ elevation. I think increasing power output way beyond spec by increasing rpm’s way beyond spec would be much more wearing on an engine than increasing rpm’s to increase power to just barely meet the factory power specs.
For me, this discussion is somewhat academic. I just finished doing the impeller mod on my 724 and that might be all the improvement I need. But, I just got a tachometer so I will increase the rpm’s too. I’d rather not mess with the governor because the gas tank has to be removed to get to it.

Thanks again for the input and conversation!


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## RC20 (Dec 4, 2019)

The only accurate answer is, it depends. 

One constant is your mix goes rich as you go higher regardless. So getting it to go 8k does you no good if the mixture is not right . It just bogs down when under load as you are not running correct mix. 

On go Karts which is a totally wrong comparison, you don't know what other mods they have done to increase flow, but you can bet the muffler and intakes have been changed a lot. Drive train will be beefed up or come that way, your blower no. He said, she said, someone said. 

Go Karter may be happy if it lasts one race, you are in this for the long term I assume (how many standby engine do they have?) 

You are also dealing with a systems that is paddle and auger speed as well as the drive-train designed around engine RPM max. 

So what you are trying to do is compare Apples to Pineapples and then saying/ sort of asking why they are not the same. Join a Go Kart group would answer your questions, Snow Blowers are not go Karts. 

You have had some good answers and not really listening - so rather than ask - just go for it and let us know how it turns out how high altitude go Karting works out.


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## Shovel (Mar 26, 2019)

dugt said:


> Sorry for the delay. I'm finally wide awake again after getting a brand new colonoscopy. (no suitable emoticon)
> 
> Thanks for the replies!
> 
> ...


Don't believe everything you read on those forums.
The valves will float before it ever reaches that 6000 RPM.
The engine will also have already reached it peak HP before that due to the cam shaft profile.
The carb is becoming a bottle neck.
The rod will be undergoing alot of stress each time it yanks the piston down for the intake stroke.
Can you build one that will run 6000 RPM.
Yes you can....but why bother..simply toss on a larger engine.
The reason they soup up these engines you are reading about it due to displacement limitations....So it's squeeze what you can out of the little engine.. it's racing.




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## 2.137269 (Nov 15, 2019)

simplest thing to do is, install a high altitude jet kit, when over 3.000 feet, no need to go crazy with engine mods,raising the rpm's, simply change the jets, 

as to hot rod'ed go karts,Jr dragsters, hot mini bikes, there are many many items we use for higher rpm's, forged cranks,billet flywheels ,rods and pistons, over sized valves, special springs, race grind cam shafts, ported heads, stinger exhausts. if the motor runs methanol one can spend upward of $5.000,00 just on the motor, like from https://www.jegs.com/i/JR-Race-Car/574/ZRE-8000/10002/-1 and that's a flat head, ohv one can go to 6k and better


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## 2.137269 (Nov 15, 2019)

anyone care to spend money on fun?? https://halfscale.com/product/nic-woods-outlaw-engine/


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## orangputeh (Nov 24, 2016)

I've got a 624 that will keep up with almost anything . may be a Honda freak. has NO modifications , no rejet , no impeller kit. Nothing.

just tuned up properly.

if you want more power do it the ol fashion way........install a bigger engine.


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## Shovel (Mar 26, 2019)

dugt said:


> At 6000' my snowblower produces 18% less power, or so I've been told. Why not increase the RPMs 18% so that the power output is about that same as it would be at sea level? If the snowblowers RPM spec is 3,500 rpm, increasing 18% would be 4,130. I'm wondering why this isn't a common mod?
> 
> Go Kart owners say the RPMs of our Honda snow blower engines can easily be increased to 6000 rpms. Higher rpms require stiffer valve springs. So, it seems Honda engines are ballanced and precision enough to handle much higher rpm's and since the increase in power is not beyond the typical power at sea level, it seems to me to have no disadvantages so why isn't it more common?


All this over speeding talk got me to doing some research last night.
I found a video from a small engine shop that had discussed setting the governor. Someone had left a comment about how you couldn't hurt the engine .
He then made another video and ran the Honda engine full out ungoverned.. RPM was 5020.
Engine life... 31 minutes.. He was very impressed .. I was also very impressed.
The moral is speed vs engine life.. How long do you want your engine to last?
That is something that you will have to decide yourself.
There is a reason the engines don't leave the factory set at five thousand RPM...Or 4500 RPM..Or 4300...A reduced engine life is the reason why.
Honda makes a great engine and will tolerate some abuse...but if you want that engine to last it is best to keep the engine speed set correctly.






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## 2.137269 (Nov 15, 2019)

orange and shovel 

thank you two for speaking the truth.. don't over rev, do properly tune


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## tabora (Mar 1, 2017)

87powershiftx2 said:


> orange and shovel
> thank you two for speaking the truth.. don't over rev, do properly tune


 Yes, they did!

Snowblowers run at pretty much a constant RPM under heavy load alternating with no-load conditions for up to hours at a time. Those high RPM karts run at varying speeds over a range of RPMs with relatively light loads for relatively short periods. In building engines, I would think the requirements for a snowblower are more like a variable speed inverter generator than a kart. High RPMs are for racing; I don't need my blower to travel at 100MPH, just want the snow to exit the chute at that speed. :devil:
Quote:
Originally Posted by *[email protected]* View Post 
_I was told torque is what gets you to (X speed) and horsepower keeps it there
So you set the engine to 3600 rpm (FAST), the augers bite into some heavy EOD, the speed drops, and the governor cranks in more air/fuel to create torque to twist all the moving parts to get back to 3600 again (or as close as possible)._


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## RC20 (Dec 4, 2019)

I don't know if you guys remember the days of Can Am where things like the Ford Mustang II raced and other comparable cars. They had that 4 cylinder Pinto engine up to 750 hp. 

Well it was a cast iron block and could take it, the mods were innumerable and they would last a race or two, but happy if they lasted the race reliably. 

Ditto the dragsters. How many have you seen blow up engines? Last a quarter mile and happy people and more so if they win. 

WWII Allison V-12, they spent years upping hp, breaking things, beefing up or new materials just to bump into another problem 100 hp latter. 300 hours running time if all went well. In the end they got upwards of 500 when the less developed beef up wise Merlin was gone at 150. 

Yami is pushing 21 years, doing fine. No I am not going to do gear 4 thorough 3 ft of snow (or two feet packed) you just use the throttle and speed to adjust to conditions and if that is a creep and it sends the snow where you want and the distance ? Done its job. 

Anyone drive a car over one of those 11,000 ft Colorado passes? I did, 4 cylinder, did ok way up there but it was not what it was down lower. Nice thing about FI is the self tuning the system does to have the mixture right. It climbed decently and did the speed limit on flats up there fine.


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## dugt (Jan 23, 2020)

Shovel said:


> All this over speeding talk got me to doing some research last night.
> I found a video from a small engine shop that had discussed setting the governor. Someone had left a comment about how you couldn't hurt the engine .
> He then made another video and ran the Honda engine full out ungoverned.. RPM was 5020.
> Engine life... 31 minutes.. He was very impressed .. I was also very impressed.
> ...


Thanks to everyone for all of the input!

I'm considering increasing the rpm's to get the engine closer to Honda spec at sea level output, not race level output or max RPM and max possible output. The example of the engine that died in 31 minutes is interesting and especially concerning if it was run without a load at 6000'. I wonder if this was at sea level or 6000' or..... Did the engine die from overheating? What was the ambient temperature? What failed? I usually use my snow blower when the temperature is below freezing. I use this HS724 on a deck that is 11' x 20' and it usually takes 10 to 15 minutes if the snow is deep. If the snow is that deep I have to go slow and the engine still bogs down closer to 2000-3000 RPMs. 

I think these engines leave the factory set at 3600 rpms because Honda wants the engines to last decades at sea level. I think they should last even longer at the reduced output at 6000' but that is based on intuition more than knowledge. My question is, at the altitude of 6000', can I increase the rpms to get higher output, which would probably still be lower output than sea level output, and still get sea level longevity?


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## 2.137269 (Nov 15, 2019)

RC20 said:


> anyone drive a car over one of those 11,000 ft Colorado passes? I did, 4 cylinder, did ok way up there but it was not what it was down lower. Nice thing about FI is the self tuning the system does to have the mixture right. It climbed decently and did the speed limit on flats up there fine.


man what a truthful mouth full. i've driven a 1981 vw rabbit na diesel up pikes peak up the old Eisenhower pass west to east. just barely made it spitting out black smoke like a old steam loco on the shoulder behind semi's doing like wise, NOT fun, 

yes on the old p51 engines, the Packard V12 -1650ci Merlin, 150 hours was good over that a wing and a prayer .remember they made 1490 hp, my dads younger brother had one after Korean war a p51d,fun to fly but big on his wallet to keep running plus it drank 100 gallons a hour of 115 to 145 av gas at top speed about 70 on cruise, but man was it fun to fly

top fuel motors one is lucky if they can make a full 1/4 mile run before blowing up or dropping cylinders, care to be sitting in front this one when it blew at 221 mph? 3/4 way though the race run 

want to race leave your wallet on the table


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## Shovel (Mar 26, 2019)

dugt said:


> Thanks to everyone for all of the input!
> 
> I'm considering increasing the rpm's to get the engine closer to Honda spec at sea level output, not race level output or max RPM and max possible output. The example of the engine that died in 31 minutes is interesting and especially concerning if it was run without a load at 6000'. I wonder if this was at sea level or 6000' or..... Did the engine die from overheating? What was the ambient temperature? What failed? I usually use my snow blower when the temperature is below freezing. I use this HS724 on a deck that is 11' x 20' and it usually takes 10 to 15 minutes if the snow is deep. If the snow is that deep I have to go slow and the engine still bogs down closer to 2000-3000 RPMs.
> 
> I think these engines leave the factory set at 3600 rpms because Honda wants the engines to last decades at sea level. I think they should last even longer at the reduced output at 6000' but that is based on intuition more than knowledge. My question is, at the altitude of 6000', can I increase the rpms to get higher output, which would probably still be lower output than sea level output, and still get sea level longevity?


The engine threw a rod.
Being at a higher altitude isn't a free ticket to over speed an engine.
As far as the reduced output from being at a higher elevation..yeah there is a loss..but it is winter so the air is more dense anyway...bringing air density back up
If your engine is bogging some going through deep snow but staying above peak torque then you are fine.
Raising your RPM will do nothing to prevent from bogging your engine down to '2000 to 3000 RPM' as you are doing..as the governor will have already opened the carburetor fully before then anyway.
Increasing your engine RPM will only cause a racing engine until you hit snow to pull the engine back down.

Seriously. Just run it at at the recommended No load speed and lug er down in the snow to about 2900 to 3000 RPM if she is struggling ...it will be fine


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## 2.137269 (Nov 15, 2019)

wanna play your gonna pay, the engine makers all sell a high altitude jet kit, simply install one, slow down your ground speed letting the machine do it's job. so what if it takes a extra 5,10 or 15 minutes to get done. 

take some time read the owners manual


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## Spawn.Qc (Dec 24, 2019)

I think you should approach higher altitudes as if it was a
Partially closed throttle... it’s not exactly the same but for the op question, the reasoning should work.

My take, you will struggle to gain power out of simply over reving due to drop of torque curve on the gx200... power is a factor of torque multiplied by revolution right?

So it comes a point where the drop in torque is too much to equal a gain while raising the RPM. 
Also, more engine rpm also means more impeller speed, which does require more power from the engine once its starts accelerating some snow from not to 100...effectively sucking away HPs that you already lack...

That’s where turbo normalized engine really shine as their turbo bring the intake manifold pressure back to where it was at sea level until a certain altitude (critical altitude)

I think the best you can do is to lean out your jet enough to make sure you are not too rich... careful to avoid being too lean as air cooled engine struggles with cooling with altitude gain... lower air density means less air molecule to absorb heat from the engine fins...

Next step, like other suggested, would be a bigger engine... it too would loose about 19% of manifold pressure so a 13 hp would produce about 10.5hp at rates rpm but better than a 6.5 becoming a 5hp...




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## RedOctobyr (Mar 2, 2014)

dugt said:


> My question is, at the altitude of 6000', can I increase the rpms to get higher output, ..., and still get sea level longevity?


As has been said, no. The extra RPMs put added stress on the connecting rod, it will make the valves want to float, etc, and this is not impacted by your altitude. 

I'd get the proper size jet for your altitude, set the governor to the max suggested RPM, and run it like that. 

If they're cheap, you could get a spare jet, and try gradually increasing the size of the jet, to see when you get the most power. But it's sort of tricky, because once the jet is too-large, you obviously can't make it smaller again, so then you can try again using the untouched jet. 

There is a thread here about re-jetting Hondas which are running lean. There might be useful info in there. You might be able to buy the recommended size for your altitude, and one with a slight-larger opening, and maybe that larger one would perform better, if Hondas guidelines are a little lean (for emissions reasons).


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## dugt (Jan 23, 2020)

Good news! I think the cable that adjusts the engine speed is too slack so full throttle is only about 80% of real full throttle. Immediately after that discovery I had to rush off but tomorrow I will adjust the cable. The blower is 15 years old so maybe the cable stretched.


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## orangputeh (Nov 24, 2016)

dugt said:


> Good news! I think the cable that adjusts the engine speed is too slack so full throttle is only about 80% of real full throttle. Immediately after that discovery I had to rush off but tomorrow I will adjust the cable. The blower is 15 years old so maybe the cable stretched.


you don't have a tach and did not know your rpms????


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## dugt (Jan 23, 2020)

I've been assuming that the correct jet for 6000' has already been installed in this HS724 because where I live the dealers that sell Honda blowers install the correct jet for this altitude when they sell them. However, I will see what jet is in it and correct if necessary. Since this is a 15 year old blower, it is pre CARB so it might be too rich. The jet in my new HSS1332 blower had a jet that was too lean even at 6000' so I already installed the correct jet for it. 

If the jet is wrong, correcting it will be icing on the cake compared to correcting the engine speed cable adjustment. I'm pretty sure I won't want to increase the RPM's after I adjust the cable.


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## Shovel (Mar 26, 2019)

orangputeh said:


> you don't have a tach and did not know your rpms????


Scarey isn't it...and he was going to turn it up without knowing what the RPM was going to be after he turned it up without a tach.

I wonder if he discovered the throttle cable issue as he was in the process of turning it up?

I am afraid this little engine may see some over speeding before it's over with.. due to the people in the kart forum telling tall tales about the RPM they are running on stock engines



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## Shovel (Mar 26, 2019)

dugt said:


> I've been assuming that the correct jet for 6000' has already been installed in this HS724 because where I live the dealers that sell Honda blowers install the correct jet for this altitude when they sell them. However, I will see what jet is in it and correct if necessary. Since this is a 15 year old blower, it is pre CARB so it might be too rich. The jet in my new HSS1332 blower had a jet that was too lean even at 6000' so I already installed the correct jet for it.
> 
> If the jet is wrong, correcting it will be icing on the cake compared to correcting the engine speed cable adjustment. I'm pretty sure I won't want to increase the RPM's after I adjust the cable.


Buy a tach that wraps around the plug wire
Springs stretch.. shafts wear.. linkages wear.. after 15 years it may need to be adjusted
If it's any consolation..I run 3450 RPM(factory setting) /208cc 24 inch..It blows snow and slush ..good enough.
Increasing my RPM isn't going to get me back in the house but 4 percent faster in real light snow ( Just short of 2 and half minutes per hour)..and even less difference if the snow is deep and I am pulling the engine down anyway.




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## orangputeh (Nov 24, 2016)

this rejet issue is confusing people with older HS models?

it could be low compression causing loss of power on older Honda's due to age and use. it could be other reasons also.


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## dugt (Jan 23, 2020)

Shovel said:


> Scarey isn't it...and he was going to turn it up without knowing what the RPM was going to be after he turned it up without a tach.
> 
> I wonder if he discovered the throttle cable issue as he was in the process of turning it up?
> 
> ...


I bought a tach and hooked it up for the first time yesterday. That is when I realized the throttle cable needs adjustment. I wasn't going to adjust the rpm's without a tach.


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## Shovel (Mar 26, 2019)

dugt said:


> I bought a tach and hooked it up for the first time yesterday. That is when I realized the throttle cable needs adjustment. I wasn't going to adjust the rpm's without a tach.


What was it running?



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## dugt (Jan 23, 2020)

Shovel said:


> What was it running?


The RPM's at "Full throttle" were 3240. If I pushed the lever into the "Choke" range the RPM's would increase to 3800. 

Today I adjusted the cable. There is only one adjustment for the cable and it is under the lever control panel. After adjusting the cable full throttle RPM's is 3840. If I push it into the Choke range it peaked at about 4500 rpms before the choke started slowing it. At this cable adjustment the idle speed is 2200 RPMs. The idle speed spec is 2050 +/- 150 rpms. The Max rpms of the HS724 is either 3600 ore 3850 rpm's +/- 150 depending on the Honda manual. 

I think my 724 will work much better and good enough with the RPM increase and the new impeller kit. It seems a little wierd to me that the RPMs increase so much when the throttle lever is pushed into the choke range but I don't think that is a problem. I won't run it in that range. 

Special thanks to those who suggested that my stock HS724 should be powerful enough. Now I think it will be.


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## orangputeh (Nov 24, 2016)

dugt said:


> The RPM's at "Full throttle" were 3240. If I pushed the lever into the "Choke" range the RPM's would increase to 3800.
> 
> Today I adjusted the cable. There is only one adjustment for the cable and it is under the lever control panel. After adjusting the cable full throttle RPM's is 3840. If I push it into the Choke range it peaked at about 4500 rpms before the choke started slowing it. At this cable adjustment the idle speed is 2200 RPMs. The idle speed spec is 2050 +/- 150 rpms. The Max rpms of the HS724 is either 3600 ore 3850 rpm's +/- 150 depending on the Honda manual.
> 
> ...


well good.if you push into the choke range you are starting to close the choke and the engine will run rich. I agree you should not run it there.


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## Spawn.Qc (Dec 24, 2019)

dugt said:


> The RPM's at "Full throttle" were 3240. If I pushed the lever into the "Choke" range the RPM's would increase to 3800.
> 
> 
> 
> ...




Sounds like something is off here... no way you are too lean at 6000ft so getting into choke range is not suppose to increase rpm.. 3250 was about 600below the factory 3800, and now that you have played with the cable you are able to get to 4500 using the choke range of the lever... which is about 600 above the factory setting of 3800.. I think you have something out of wack in the throttle/governor linkage... choke range isn’t supposed to have any effet on high speed idle rpm... it can play on rpm under load as it will enrich your mixture.. unless you where terribly under jet, which is never gonna the case at 6000ft.. wait wait wait.. is you jet partially clogged?? If not the main jet maybe your idle jet.. could you post a picture of your spark plug after you have let it fast idle for a minute or two? And one after it’s been ran under load ?


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## dugt (Jan 23, 2020)

Spawn.Qc said:


> Sounds like something is off here... no way you are too lean at 6000ft so getting into choke range is not suppose to increase rpm.. 3250 was about 600below the factory 3800, and now that you have played with the cable you are able to get to 4500 using the choke range of the lever... which is about 600 above the factory setting of 3800.. I think you have something out of wack in the throttle/governor linkage... choke range isn’t supposed to have any effet on high speed idle rpm... it can play on rpm under load as it will enrich your mixture.. unless you where terribly under jet, which is never gonna the case at 6000ft.. wait wait wait.. is you jet partially clogged?? If not the main jet maybe your idle jet.. could you post a picture of your spark plug after you have let it fast idle for a minute or two? And one after it’s been ran under load ?
> 
> 
> Envoyé de mon iPhone en utilisant Tapatalk


Tomorrow I could post a photo of the plug after fast idle. Under load could take a few weeks because it is forecast to be dry here for at least three weeks. 

In the meantime I could clean both jets and see if it runs differently afterward.


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## Shovel (Mar 26, 2019)

orangputeh said:


> well good.if you push into the choke range you are starting to close the choke and the engine will run rich. I agree you should not run it there.


Something is wrong and needs to be fixed for sure.

I still know the over speeding is tempting but these splash engines are at a disadvantage right from the start.
Do they work... Yep and that is all you can say for them.
Example.
You know not to overfill your car engine with oil... As the cranks whips the oil which aerates the oil... These splash engines are doing just that .
The faster it is run the more it whips the oil.
The rod isn't passing through 'solid' oil to begin with as a result
It's gets worse..when the rod slices through the oil there is a brief cavity formed that has to be refilled by gravity.
At 3600 RPM that is 60 times a second already.. The oil at that engine speed barely has enough time to refill the cavity as it is.
The faster we run these engine the less oil the rod gets...and that oil is also more aerated as well
It gets worse...The force of the piston and rod quadruples when speed doubles. This is why 'strokers' run at lower RPMs
So now with high RPM on a splash engine we are receiving less oil to the rod but actually need more of it.. and what reduced quantity we have has to keep the film up while it is in a more demanding condition /all while the oil is more aerated condition.
It gets worse we run 5 /30 oil.. This oil is loaded with viscosity index improvers.
It's a 5 weight oil.. There are additives(strands) which change shape with temperature.. that is how it gets the 30 rating.
Those strands line up in between the bearing and crank reducing it's ability to actually act as 30 weight.. that is why 5 30 is not recommended for substained high speed driving.
In our case the rod is the also the bearing but it also suffers the same problem.
So we are using not the greatest oil for the application.. but we have to for cold starting.
The oil is being whipped.
The faster the RPM the more whipping.
The faster the RPM the less oil the rod receives as it passes through a larger void.
The demands are higher at higher RPM ..while higher RPM in a splash engines works against us to oil the rod to crank surface to begin with.
We are using oil not rated for substained high speed usage.
Everything is working against you/ and the higher the RPM the more it works against you. 
It can not be stressed enough DO NOT OVER SPEED these style engines.
At specified RPM we can get hundreds of hours of operation out of them sometimes.
A small reduction in RPM helps to negate the problems above and increases the engine life in the rod to crank surface.
An increase in RPM compounds the problems listed above and can drastically shorten the life of the engine.



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## rfw1953 (Oct 11, 2017)

I live in the Central Rocky Mountains at 9561' elevation. My Honda is in its 4th season and doesn't miss a beat at this elevation. My attitude is if it's not broke, why fix it??? :wink2:


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## Shovel (Mar 26, 2019)

rfw1953 said:


> I live in the Central Rocky Mountains at 9561' elevation. My Honda is in its 4th season and doesn't miss a beat at this elevation. My attitude is if it's not broke, why fix it??? :wink2:


I would need Oxygen ..I couldn't operate the snowblower even though it's willing.
At that elevation and in the cold... If it starts it's a good one lol



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## dugt (Jan 23, 2020)

Shovel said:


> Something is wrong and needs to be fixed for sure.
> 
> I still know the over speeding is tempting but these splash engines are at a disadvantage right from the start.
> Do they work... Yep and that is all you can say for them.
> ...


Thanks for that detailed explanation! I knew none of that. 

I don't want to over rev my engine anymore. Now that it is up to spec it should be powerful enough. Plus I have high expectations of the impeller mod. I didn't mention this before but this 724 was barely throwing snow far enough to get it over the deck railing and onto my driveway. Then I would have that much more snow to blow off of my driveway. Now 724 will probably blow snow far enough to make it to the sides of my driveway so I don't have to blow it twice. (That last part sounds like something a hooker would say.)


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## dugt (Jan 23, 2020)

Spawn.Qc said:


> Sounds like something is off here... no way you are too lean at 6000ft so getting into choke range is not suppose to increase rpm.. 3250 was about 600below the factory 3800, and now that you have played with the cable you are able to get to 4500 using the choke range of the lever... which is about 600 above the factory setting of 3800.. I think you have something out of wack in the throttle/governor linkage... choke range isn’t supposed to have any effet on high speed idle rpm... it can play on rpm under load as it will enrich your mixture.. unless you where terribly under jet, which is never gonna the case at 6000ft.. wait wait wait.. is you jet partially clogged?? If not the main jet maybe your idle jet.. could you post a picture of your spark plug after you have let it fast idle for a minute or two? And one after it’s been ran under load ?


The main jet is perfectly clean. I couldn't get the brass part out that resides above the main jet to fall out but I suspect it is clean since everything else I checked was clean. The float bowl and sediment bowls were very clean. I'm going to leave the engine as it is. 

The jet is a 75. That might be one size too big for this 2005 HS724 at 6000'. After I we get snow I will run it under load and then check the plug to see if was running rich or not.


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## Shovel (Mar 26, 2019)

dugt said:


> Thanks for that detailed explaination! I knew none of that.
> 
> I don't want to over rev my engine anymore. Now that it is up to spec it should be powerful enough. Plus I have high expectations of the impeller mod. I didn't mention this before but this 724 was barely throwing snow far enough to get it over the deck railing and onto my driveway. Then I would have that much more snow to blow off of my driveway. Now 724 will probably blow snow far enough to make it to the sides of my driveway so I don't have to blow it twice. (That last part sounds like something a hooker would say.)


Odd as the Honda's usually blow pretty good.
The impeller mod ..while always helps..it doesn't help as much on a Honda as they usually have a smaller gap anyway..Part of the reason they toss good to begin with.
Those RPM must have really been dropping on you..If it still is crippled after getting the speed set..check for loose or glazed belts.
Fine machines...just needs it 15 year maintenance lol.



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## orangputeh (Nov 24, 2016)

Shovel said:


> Odd as the Honda's usually blow pretty good.
> The impeller mod ..while always helps..it doesn't help as much on a Honda as they usually have a smaller gap anyway..Part of the reason they toss good to begin with.
> Those RPM must have really been dropping on you..If it still is crippled after getting the speed set..check for loose or glazed belts.
> Fine machines...just needs it 15 year maintenance lol.
> ...


ya people don't bring in their Honda's for service unless something is broke. last month got a HS828 that never has been serviced since new. that's 28 years old. guy told me "nothing ever went wrong with it"

before starting it went to check oil and the owner said " oh, that's where you check the oil.". so the oil was 28 years old also. it was only down about 5 ounces . it did need new belts and bearings but was surprisingly good condition. the owner did use good gas and always treated it. I pulled the carb apart and could not believe how clean it was.


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## RC20 (Dec 4, 2019)

I am not that bad but mine gets ignored a lot if you will. I have been meaning to check the valves since I bought it!


I do run it at the lowest RPM that does the job. 


Some Truism that mechanics (machinery and building controls tech/engineer and generators/fire pumps for 35 years) 

Oil is about due, every 5 years, run synthetic. Really don't get that many hours each winter. 

I got new belts for it 5 years ago and then checked them. The new belts are still hanging in the shop. The old ones were like new. 

The Toro need a lot more attention, belts, bearings, I think I replaced the drum (too long ago)


Still pretty much if you keep an eye on the oil and a quick check they are amazingly durable on the good ones (I would put Toro up there, Yami as well and Honda, never had an Ariens but they seem in that class.


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## dugt (Jan 23, 2020)

I was curious why my HS724 was reving up to 4500 rpm when I moved the throttle into the Choke zone so looked into it and found that the max throttle set screw was set too loose. I screwed it in a few turns and now goes to 3600 rpms at max throttle and doesn't go higher than 3600 in the Choke zone. 

I also tightened the auger belt a little and lowered the idle rpm to spec. Now I have total confidence that it will work real well.


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## Shovel (Mar 26, 2019)

dugt said:


> I was curious why my HS724 was reving up to 4500 rpm when I moved the throttle into the Choke zone so looked into it and found that the max throttle set screw was set too loose. I screwed it in a few turns and now goes to 3600 rpms at max throttle and doesn't go higher than 3600 in the Choke zone.
> 
> I also tightened the auger belt a little and lowered the idle rpm to spec. Now I have total confidence that it will work real well.


All you need now is snow...May mother nature dump a foot of snow on you please



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## 2.137269 (Nov 15, 2019)

orangputeh said:


> ya people don't bring in their Honda's for service unless something is broke. last month got a HS828 that never has been serviced since new. that's 28 years old. guy told me "nothing ever went wrong with it"
> 
> before starting it went to check oil and the owner said " oh, that's where you check the oil.". so the oil was 28 years old also. it was only down about 5 ounces . it did need new belts and bearings but was surprisingly good condition. the owner did use good gas and always treated it. I pulled the carb apart and could not believe how clean it was.


service unless it's broke is right. 20 year old machine in the shop saturday,never ever serviced, complaint was no start i can't pull the cord, question, when was it serviced last? been sitting for 6 years ,spitting his chew into a coffee cup. 

item 1 can't pull the hand cord, evict mini and family , replace the chewed up ign,coil. item 2 gas tank smelled like turpentine. flush the tank, item 3 clean out the carb, gummed solid, item 4 adjust the tight valves, item 5 flush the sludge out of the block. 4 times with kero. item 6 a new set of belts,


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