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How do I tune the 'EPA' carburetor on Husky 3120

Started by chainsaw_louie, March 09, 2004, 05:20:12 PM

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chainsaw_louie

I've run my new 3120xp for about 10 hours now and the owners manual says  

"The carburetor is set to its basic settin when test run at the factory. The basic setting is richer than the optimal setting and should be kept kept during the machine's first working hours. Thereafter, the carburetor should be finely adjusted. Fine adjustment should be carried out by skilled technician."  (Gee thats helpful)

They also say "after 10 tanks of fuel the saw has been 'broken in'.  To ensrue that your saw is at its peak performance and after break in, have your dealer, who has a revolution counter, to adjust the carburetor for optimum operating conditions."

Now, on this EPA 3120 xp, there are just 2 adjusting screws, a L=low speed needle and T=idling speed adjustor
There is no H-high speed needle

So, my burning question is how do you adjust the high speed setting or how does the dealer do it.  I want to be able to do it myself or at least know that it is done correctly by the dealer since he may not get many of these saws in his shop.

The manual says  
"this saw is equipped with a caruretor that has an integrated, fixed high speed jet"  

Am I correct to conclude that the only adjusting I need to do is the idle mix and the idle speed, all the rest is preset and thats it?  No adjusting the H screw at wot till it slightly 4-cycles?  Please advise.

Tim


Kevin

The initial setting for low speed is 1 1/4 turns out from lightly seated, final adjustments when warm and running.
Low speed mixture screw is adjusted to obtain highest idle speed then turn the screw 1/4 turn counterclockwise.
If the engine hesitates on acceleration adjust the screw.
Adjust the idle speed screw so engine idles just below clutch engagement.
There is no high speed adjustment.
Get a tach if you want to get it right.

Rocky_J

I've had some experience with fixed jet saws, had an 026 with fixed high speed jet. Never could get it right, even after changing out the tiny internal jets a few times. By the time I got smart and bought an adjustable carb, the damage was already done and the piston had been scored from running too lean. Of course, the warranty was already up. I was so PO'ed I gave the saw away and bought a 346XP Husky (with adjustable jets).

For a thousand dollar chainsaw, I'd darn sure insist on being able to adjust the carb properly. My suggestion is to replace the fixed jet carb BEFORE you have issues with it. If you run it too lean, it will slowly burn up your saw and you will have no recourse when it seizes a month after the warranty expires.

chainsaw_louie

Well on the other hand, I figure for an expensive saw it should have a set up that works.  Two years is a long time for some saws and a lot of fuel can be burned up in that time. They got to have a system that delivers power and reliability with the stock setup.

I'm guessing here but wouldn't the EPA be encouraging the saw makers to run the engines not too rich because a rich settings produces a dirtier burn with higher emissions.  The question here is just what is the setting that the EPA carb is preset to and is it rich enough to properly lubricate the piston and sleeve. My experience is very limited, is replacing the carbs on these saws a standard thing to do for the professional user??  The downside is that the warrantee is void when a stock part is swapped out.

Rocky_J

I was merely suggesting using the carb for an older 3120 instead of the newest EPA mandated carb. Yes, you would think a $1000 saw SHOULD work properly, but the saw makers are being pinched b y the EPA standards and must make changes which drastically affect the life and performance of the saw in order to meet the strict emissions standards.

Your saw was designed to make at least 2-3hp more than what the current model produces. Much of this power and performance can be realized simply by undoing the EPA mandated restrictions. Reliability and engine life are shortened by overheated motors with not enough fuel to lubricate or cool properly. The EPA would just as soon not let us run chainsaws at all. But I'll shut up now and let you do what you wish with your $1000 saw.

oldsaw-addict

If it was my $1000 saw I would replace the "EPA" carb with one that is FULLY adjustable, not just adjustable on the low speed needle.I have a tendancy to tune my carbs a bit rich on the high end rpm settings that way I know I'm getting enough fuel to the engine and I'm not runnign it too lean or anything else that would reduce the lifespan of my saw. I work hard for my money, I dont wanna spend it on repairs that could have been avoided by simply swapping out a carb in the saw. Of course this is IF it were my saw, but its your saw so its your choice here, I'll step back and close my mouth now so I dont say anything I'll regret later. you now have my 2 cents worth on the matter.
Let there be saws for all mankind!

chainsaw_louie

Thanks, I appreciate the input. I've read the horror stories about ruining a 2 cycle engine by having too lean a carburetor setting I wanted to be sure that didn't happen to me.  It was only after I carefully read the operation manual did I realize that there isn't a High speed jet on this saw.  I probably should have read it before I started using the saw but was too eager to start making lumber,  in a way its good that it came adjusted correctly from the factory.

I've done some asking around (Madsen's, Procut etc) about what people are doing with these EPA equipped saws and I keep hearing that people are using them the way they are.  The manual makes it sound like the dealer will do some adjusting with the fixed High speed jets, but the fella at Madsen's says they only adjust the low speed jet and the idle. I know next to nothing about how these new EPA saws are handled with regard to the carburetor setting/warrantee but I am getting the idea that the only way the manufacturer can protect themselves (not have to give away too many free saws) and make the EPA happy is to go with the fixed jet carburetor.

So if I stay stock with this saw,  and by increasing the oil in my fuel mix shouldn't I be able to guarntee good lubrication to ensure long saw life.  From what I've read the fuel mix in new saws has less oil than previously. It wasn't always 50:1 mix?  I wonder what has changed that makes less oil in the fuel possible and is 50:1 really enough oil or is this a EPA standard too?

By the way, if you shop around its possible to find a new 3120xp w/36" bar for $850 or so.  Still its enough $ to make me want to have it last a long time.  For a single cylinder engine with very few parts - no gears, valves, cam, electrics - they sure do charge a lot.  

oldsaw-addict

I dont know about the 50:1 fuel oil mix being an industry standard, but I do know that I dont use 50:1 in my 670, I use a mix thats 40:1 or 32:1 ratio in my chainsaws, that way I KNOW I'm getting enough oil in the crankcase and it has sufficient lubrication. Also use a FULL synthetic 2 stroke oil in your fuel oil mix instead of the synthetic blend used by the manufacturers.
Let there be saws for all mankind!

Corley5

With your saw still being under warranty you'd better run Husky two cycle mix in it.  They can't say much if it's mixed right and something goes wrong if you're using their oil.  Mixing it rich won't hurt it any and if the mosquitoes and black flies are out it's a good idea but not necessary.
Burnt Gunpowder is the Smell Of Freedom

archerR80RT

Just my opinion, but if I had a fixed jet saw, or a fixed jet anything with a two cycle engine, I would not adjust the oil mixture. I would run it at 50:1 and be happy. If you change the oil mixture, you will in effect change the jetting. Oil has a specific gravity that is heavier than gas, so if you increase the oil to gas ratio you are actually leaning out the mixture as the mixture will be heavier and not venturi as much mixture into the engine. Although the amount is slight, It could make a difference in a fixed jet engine. Also the fact that oil burns hotter than gas so you also up the temp by doing this, which is another battle in its own. I'm not trying to start a war, just go with the 50:1, and your saw will more than likely be fine. gary

chainsaw_louie

Thanks for all the helpful suggestions.  Since I don't know a lot about what it takes to keep one of these engines running over the long haul, I was concerned that if I wasn't careful, by not keeping it in tune, I could 20 lbs of scrap aluminum alloy instead of a chainsaw.  I guess thats still true but it seems like I really dont have to do much to this saw, just put fuel in it and run it. The carb setttings are fixed like the mfg wants them and will back it up if it goes bad.  What I think I will do is to write on the plastic cover, with a magic marker the date when the warantee expires.  Then, before that day I'll examine the cylinder walls and take it to the dealer if for any reason there is scoring and let them replace the piston and cylinder per their warantee and fixed carb settings.  

Well, its Saturday am and I am off to Pennsylvania with the mill to make some cherry and walnut lumber.  Thanks for all the advice.

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