Todays small engines

[Giles]

I have worked on small engines for over fifty years, and I have seen a lot of changes.
The last chainsaw that I bought new, was a 1980 Husqvarna 40. I wore out three bars and countless chains and rebuilt the carburetor two or three times. It still runs like new and engine hasn't been into.
The point I am trying to discuss is the fact that I never had to periodically adjust the carburetor. Each time I rebuilt/cleaned the carb, I would just return the screws to where they were.
I found this to be true with lawnmowers as well.
With any of todays saws, even a change in brands of gasoline or oil will likely change the carb settings.
I am referring to muffler and carb modded saws and other small engines, but more so with chainsaws.
Do any of you have the same memories and why do you think we have to really watch carb settings today?

 

[CountryBoy19]

With any of todays saws, even a change in brands of gasoline or oil will likely change the carb settings.

It used to be that gasoline was gasoline. With ethanol blends, and ethanol having ~70% of the BTUs of gasoline, the amount of ethanol in the fuel can effect Air-to-Fuel Ratio on your engines. Your car doesn't notice because it has O2 sensors that adjust the fuel map based upon unburned oxygen in the exhaust (indicator of lean running). Your saw doesn't have this. With the method of blending, various stations/brands carrying different amount of ethanol, it's wholely unreliable to count on your pump gas having 10% ethanol as the sign on the pump says. As a matter of fact, that sign likely says, "May contain up to 10% ethanol". Some have found pump gas to contain even more than that in some isolated circumstances.

Essentially, it's a crap-shoot what you get. If you can run ethanol free gas I would suggest you do so just to avoid that issue entirely...

ETA, to clarify: It's not that the ethanol is causing problems with you engines, it's that the unknown amount of ethanol is changing your AFR and you have no way of knowing/predicting it so you must readjust each time you get new gas. Removing ethanol from the gas completely just removes the uncertainty of how many BTUs/gal your fuel is (normal gas can be pretty much nailed down to a narrow range except seasonal blends may vary slightly more).

 

[Giles]

It used to be that gasoline was gasoline. With ethanol blends, and ethanol having ~70% of the BTUs of gasoline, the amount of ethanol in the fuel can effect Air-to-Fuel Ratio on your engines. Your car doesn't notice because it has O2 sensors that adjust the fuel map based upon unburned oxygen in the exhaust (indicator of lean running). Your saw doesn't have this. With the method of blending, various stations/brands carrying different amount of ethanol, it's wholely unreliable to count on your pump gas having 10% ethanol as the sign on the pump says. As a matter of fact, that sign likely says, "May contain up to 10% ethanol". Some have found pump gas to contain even more than that in some isolated circumstances.

Essentially, it's a crap-shoot what you get. If you can run ethanol free gas I would suggest you do so just to avoid that issue entirely...

ETA, to clarify: It's not that the ethanol is causing problems with you engines, it's that the unknown amount of ethanol is changing your AFR and you have no way of knowing/predicting it so you must readjust each time you get new gas. Removing ethanol from the gas completely just removes the uncertainty of how many BTUs/gal your fuel is (normal gas can be pretty much nailed down to a narrow range except seasonal blends may vary slightly more).

" Essentially, it's a crap-shoot what you get. If you can run ethanol free gas I would suggest you do so just to avoid that issue entirely..."

Never run anything but non-ethanol 93 Octane Gasoline, But I agree you can't be sure of the Ethanol content.

 

[Bigg_Redd]

Just a guess here, but, I'd bet the changes you're referencing are a result of our ever more ridiculous emissions standards.

 

[pma1123]

Agreed ^^^ Manufacturers are making this stuff run lean right out the door to meet emission requirements. They're doing it at the elevation and temperature of the manufacturing test cell also, not where the consumer is using it.

Last saw I bought, before I ever pulled the cord I did the mods to the mixture screw limiters and first cuts were making sure the saw was not going to burn itself down. Another variable not mentioned is the difference in air density between a 70F day, and a 5F day. You need a lot more fuel out in the cold to match that dense air. That same saw which ran like a scalded cat in 5F weather needed a 1/4 turn leaner (H) once the weather warmed up so it was not having rich-burble at WFO under load.

 

[CountryBoy19]

I have to agree with the above: if you're already running non-ethanol fuels then it mostly mitigates the BTU/gallon issue. I bet it's a combination of emissions crap (limit tabs on carbs) and varying weather (air density)...

 

[Highbeam]

Are you sure you're not just being too picky? Trying too hard for constant jetting perfection? I propose that you could just find a decent setting and just run it.

 

[colin.p]

I just bought a new saw from a local Husqvarna/ Dolmar/Echo dealer and got the 3 cans of fuel to supposedly double the warranty to 4 years. It would probably take me a year to use the fuel, as I don't really use the saw that much, but it's always nice to have it around when I really need it. I didn't do anything with the carb as it's under warranty and obviously cutting tabs off would cancel that.

I was just in the shop, buying a head gasket for my lawn tractor, and I asked him about the carb settings and should they be re-adjusted after a time.. He said not to worry about it. Now that would seem to go against what most people (on this and every other wood forum) say. However, the vast majority of people who buy a saw, never go to forums, and just run the saw with the proper gas/oil mix and proper maintenance and don't even think about carb settings. Unless something is wrong with the saw, or they screw something up themselves, the saw lasts for a long time.

Now if the saw manufacturers were setting the carb settings to a point that would cause premature failure (to appease the EPA) , wouldn't they and the EPA be held responsible to some sort of degree?

 

[jaoneill]

I bought a new pro-model Jonsered about this time last year and the dealer had me bring it back in after a breakin period of 20 hours. He tweaked the settings (I'm guessing leaned it up) and I haven't touched it since. That said, I burn nothing but E-free gas.

 

[Corey]

Certainly a lot of things seem to play into the mix. Changes in gasoline, stricter emissions, better performing saws, etc. I suspect 'back then' saws were a little lower power for a given size and probably ran rich, with ignition somewhat retarded from optimal. So even if changes made the mix a little more rich, or a little less rich, it was still rich enough to run.

Today's saws likely make much more HP per cc, better emissions, better fuel efficiency, etc. They are likely tuned to be nearly 'ideal', so if there are small changes in fuel, atmosphere, temperature, etc, they could go over the 'perfect' mark and start to run lean. I guess one way to look at it, back in 1900, a "4hp" engine was likely 800 pounds of cast iron, two big flywheels and a cart to wheel it all around. In 2000, a 4hp engine is likely 10 pounds (or less) of magnesium and aluminum you carry with one hand. So if it needs a bit of carb adjustment to maintain that performance, that might be the trade-off.

Conversely, you mention 3 carb rebuilds on a 35 year old saw...so perhaps major maintenance every 10 years on average? Thinking back across all the years and small engines I have, I don't know that I've ever done a carb rebuild. The last thing I specifically recall was an 84 Oldsmobile my wife had at the time and that rebuild was in '00. I did also "rebuild" a '96 jet ski carb in ~'08, but that was really a filter replacement/cleaning as opposed to anything major with the carb itself.

Of course I don't make a lot of carb adjustments, either. I generally tune the saw to run good in the cool/dense air of fall, and if it richens up a bit in the hot / thin air of summer, that is likely just enough to cool it down a bit, anyway. Plus all my cutting is done within a couple hundred feet elevation change, so no worries about running up a mountain, down a valley, etc.

 

[Ashful]

Are you sure you're not just being too picky? Trying too hard for constant jetting perfection? I propose that you could just find a decent setting and just run it.

I don't think that's it. After all...

I never had to periodically adjust the carburetor. Each time I rebuilt/cleaned the carb, I would just return the screws to where they were.

 

[Highbeam]

With age comes more time and mental patience for tinkering and optimizing. I used to be happy with pepperoni pizza and I've since optimized the experience to include about all ingredients.

I betcha that despite the apparent need for fine tuning, each of the OP's engines starts, runs, and works.

 

[Oldman47]

I just bought a new saw from a local Husqvarna/ Dolmar/Echo dealer and got the 3 cans of fuel to supposedly double the warranty to 4 years. It would probably take me a year to use the fuel, as I don't really use the saw that much, but it's always nice to have it around when I really need it. I didn't do anything with the carb as it's under warranty and obviously cutting tabs off would cancel that.

I also recently bought a husky with 3 quarts of fuel for the extended warranty. On my 555 the first can is gone, 5 small trees are down and are bucked to length. I started working on that second can last evening and dropped a 6 inch and an 8 inch DBH tree and bucked them to length. I am cutting down fence wreckers and still have 4 more to go. Damned birds. I wish they would crap tree seeds somewhere else.

 

[jebatty]

Seems to me that CountryBoy 19 likely nailed it: the problem is inconsistent gasoline from the oil companies. If the oil companies would provide a consistent mix, the "problem" would largely disappear. That said, my old Stihl 026 which I bought in October 1996 always runs like a charm, and a lot of fuel changes have occurred since then. Similarly with my Husky 372XPG bought in October 2002. With both I always use non-ethanol premium gas with stabilizer and a 50:1 mix.

The other nails out there just as likely are the saw manufacturers in putting on the market cheap saws. Us good old Americans shop low price, lower price, and lowest price. If the focus was more on quality, we would find high quality -- and the price would reflect that. The Stihl cost me $446 in 1996, and the Husky was more than $600. Both are solid saws in every respect. In today's dollars, the little Stihl would be about $670 and the mid-sized Husky would be about $850. Buy quality and the "problems" disappear.

 

[Ashful]

Plenty of folks buying real saws at $700 - $1200, here. Pro saws in the hands of firewood cutters.

I have trouble believing that the manufacture of billions of gallons of gasoline is anything but a very tightly controlled process. The economics of scale simply demand that. It's more likely that formulation drifts in storage, due to effects such as differing evaporation rates of the various compounds involved.

 

[Oldman47]

If you buy gas in winter, at least around here, it contains far more volatile fraction than summer fuel. The end result is that more of the light fraction evaporates off in storage. Summer fuel, at least in the northern part of the country, is more stable in storage than winter fuel. It is not a question of "quality" but rather a question of economics. When EPA regulations allow more volatile components in raw fuel, they are included in the blend that you buy. No amount of "pure gas" rhetoric will change that. Alcohol does not affect the way these refiners blend fuel for summer vs winter.

 

[CountryBoy19]

Plenty of folks buying real saws at $700 - $1200, here. Pro saws in the hands of firewood cutters.

I have trouble believing that the manufacture of billions of gallons of gasoline is anything but a very tightly controlled process. The economics of scale simply demand that. It's more likely that formulation drifts in storage, due to effects such as differing evaporation rates of the various compounds involved.

You better believe it. "tightly controlled" to you may not mean the same as "tightly controlled" to the next guy. And often times "tightly controlled" means they fix things when they are out of spec, but they don't necessarily recall things that aren't in spec.

The blending of the ethanol into the gasoline does NOT take place at the refinery, it takes place at the fuel depot or at the pump through a "blender pump". Neither of these is a "precisely controlled process" and therefore the actual amount of ethanol you get can be varied. Above and beyond that, as you mentioned, non-ideal storage conditions, bad day at the refinery (things often do go wrong and sometimes bad product slips out), etc can all play a role in the fuel you get. The reason it's not an issue for 99.9% of people is that they are using the fuel in a modern automobile that has sensors, gauges, and computer controls that ALL act together to counteract the problems that may arise. Your chainsaw doesn't have those so if you pay attention you may notice subtle differences...