# Chainsaw Carburetor Tuning 101



## MasterMech (Mar 1, 2013)

Had to tune the MS460 anyways after a carb cleaning.  Good opportunity to show how it's done from scratch.


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## DexterDay (Mar 1, 2013)

What about that DP Muffler??  (stock...  No thanks)  

That looked and sounded good. Great job MM. Loved that rebuild thread. Now run the chit out of that thing


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## Nixon (Mar 1, 2013)

Sounds really healthy ! She's oiling well too .


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## kenskip1 (Mar 1, 2013)

I would have made a cut or two in order to make sure the engine got to full operating temperature prior to making adjustments.However that is my personal preference, Ken


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## Boog (Mar 1, 2013)

MasterMech said:


> Had to tune the MS460 anyways after a carb cleaning. Good opportunity to show how it's done from scratch.


 
Nice job MM. I need to get a tach...............I try to do the exact same thing by ear.............only I'm totally deaf in one ear since "78". Its obviously touch and go!

Your oiler is working good too .


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## HDRock (Mar 1, 2013)

That's great  Now now do one , explain and use no tach ,please


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## ArsenalDon (Mar 1, 2013)

Talent....It honestly is talent. I coach soccer for a living and talent is not easy to find..you are a natural


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## Senatormofo (Mar 2, 2013)

I'm impressed! You really know your chit about tuning these saws!


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## MasterMech (Mar 2, 2013)

DexterDay said:


> What about that DP Muffler??  (stock... No thanks)
> 
> That looked and sounded good. Great job MM. Loved that rebuild thread. Now run the chit out of that thing


 
I'm not done with that thread yet. And yes, the DP muffler is on there. Final pics are coming if the starter I want to use _ever_ gets here.



Nixon said:


> Sounds really healthy ! She's oiling well too .


 
And that's with the oiler @ roughly 50%.


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## MasterMech (Mar 2, 2013)

HDRock said:


> That's great  Now now do one , explain and use no tach ,please


Why no tach?  You can tune by ear only too.  Forget I'm using a tach and listen to what's going on.


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## MasterMech (Mar 2, 2013)

kenskip1 said:


> I would have made a cut or two in order to make sure the engine got to full operating temperature prior to making adjustments.However that is my personal preference, Ken


That saw was "pre-warmed". 

EDIT: I had run the saw a bit before the carb was cleaned.  Cleaned the carb, ran it again but it was way lean. Went back inside to answer the call of nature, and apparently it had cooled enough to require the choke. Normally I would do a tune with the saw warmed up more bu this one was far enough out (lean) that I didn't want to cut with it for very long.


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## HDRock (Mar 2, 2013)

MasterMech said:


> Why no tach? You can tune by ear only too. Forget I'm using a tach and listen to what's going on.


I here ya


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## HDRock (Mar 7, 2013)

The new Husky 445 refurb
Don't know if I am very good at tuning, also at the time I couldn't see in the holes , is the idle adjust screw the same head as the H and L ?
I will check things out some more tomorrow, got dark on me, anyway, the vids


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## MasterMech (Mar 7, 2013)

The audio breaks up too much for me to really hear whats going on.  Can your hear it four-stroking at WOT?  It should have a rough tone that will smooth out as soon as you put it in the wood.


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## HDRock (Mar 8, 2013)

MasterMech said:


> The audio breaks up too much for me to really hear whats going on. Can your hear it four-stroking at WOT? It should have a rough tone that will smooth out as soon as you put it in the wood.


 
Ya your right the audio is breaking up, yes I can hear it four-stroking at WOT, before I adjusted it it was four-stroking almost the whole throt range.
I tuned my 2 older smaller saws and it seems it was easier to tell  the difference while adjusting, the 445  ran smooth cutting, just don't want to have it running lean.
I have to spend more adjusting it, at end of second vid I think I had it idling to fast.
On the L needle I could here the difference good,and I think, I got it in the middle ground pretty good ,but at WOT with H needle hard to tell


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## STICK (Mar 10, 2013)

*I FOUND THIS ADVICE*
It seems to work well without a tach. But, what do I know, I am just a cowboy with a bag of tools.
This is routine operator maintenance.
*1. *Start your saw and run it for a few minutes to warm it up.
*2. *Set your saw down, let it idle for 30 seconds, and then pick it up and tip it forward (handle up and bar down).
*3. *If it keeps running, go to Step 4. If it stalls, tighten the *Low Speed* screw. This will reduce the amount of fuel entering the carburetor. Repeat Step 2 as necessary.
*4. *Rev (accelerate) the idling saw.
*5.* If it accelerates fine, go to Step 6. If it “dogs,” loosen the *Low Speed* screw. This will increase the amount of fuel entering the carburetor. Repeat Step 4 as necessary.
*6. *Rev the idling saw for about 5 seconds (never rev it for 10 seconds or longer).
*7. *If it “flutters” while being revved, this is good, so go on to Step 8. If it “screams” while being revved, this is bad. Loosen the *High Speed *screw. Repeat Step 6 as necessary.
*8. *If the chain is stationary while the saw idles, you’re finished.
*9. *If the chain rotates around the bar while the saw is idling, adjust the *Idler Screw* as necessary to make it stop. This situation can be fixed in a matter of seconds and is extremely dangerous if not corrected.
That’s it. Less than five minutes of your time can make a big difference in how well your saw runs. Two additional tips are 1) use hot water and dish soap to clean a paper-type air filter (let it dry before using), and 2) use chainsaw gas to clean a wire-type air filter (you don’t need to let it dry before using).
This information will help your saw run more effectively and efficiently.


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## MasterMech (Mar 10, 2013)

STICK said:


> , I am just a cowboy with a bag of tools.


 
Then perhaps there is something to be learned from the professionals.


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## brian89gp (Mar 10, 2013)

What if you have a saw that otherwise runs perfectly but it will die when you let off of the throttle after in a cut.  Doesn't die if you are just revving.  Also it doesn't die after a cut if you feather the throttle once or twice before letting it idle.


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## osagebow (Mar 10, 2013)

MasterMech said:


> Then perhaps there is something to be learned from the professionals.


 
Question for ya Mech - will the spline tool for a MS 290 (I know I'd have to fool with the tabs to get to it) be the same one as a Husky 350?


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## HDRock (Mar 10, 2013)

I think I got the 445 dialed in pretty good, starts good, idles fine, revs up good, four strokes at full throttle, and I put it in some 15" di ash, using the dogs it only bogged out when I pushed it too hard, and the saw did cut pretty well, as long as I let the saw do work, and that is with a low Pro chain on it that came with it, I will use that until it gets dull then put the new chisel chain on, or maybe I should take the low Pro off now and just use it for backup

Edit: I still think am going to get me a tech tac tt 20k


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## HDRock (Mar 10, 2013)

I do like the splined tool, very easy to slip In and onto screw head, used a marker and put a line down the shaft so I could tell how far I was turning it, but mostly just did it by ear


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## STICK (Mar 10, 2013)

MasterMech said:


> Then perhaps there is something to be learned from the professionals.


 
Surely so. That is why I am here.

Please, Do tell.


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## OldLumberKid (Mar 10, 2013)

MasterMech said:


> Had to tune the MS460 anyways after a carb cleaning. Good opportunity to show how it's done from scratch.






Dumb question but can it be done with the bar and chain off, or does it have to be under load (of a rotating chain)?


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## MasterMech (Mar 10, 2013)

OldLumberKid said:


> Dumb question but can it be done with the bar and chain off, or does it have to be under load (of a rotating chain)?


 I supposed there is no reason you couldn't do it sans bar & chain, but adding the B&C would change the load and I would check it by ear at least before trusting it.  I haven't done one that way but I would expect it to significantly affect the top end RPM setting.


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## MasterMech (Mar 10, 2013)

brian89gp said:


> What if you have a saw that otherwise runs perfectly but it will die when you let off of the throttle after in a cut. Doesn't die if you are just revving. Also it doesn't die after a cut if you feather the throttle once or twice before letting it idle.


 
There are a couple things that could aggravate that but I'd definitely try a retune. For a quick test, back the L screw out 1/4 turn and run the saw.  If it stops stalling or significantly reduces how often it does stall, then clean the muffler screen and air filter thoroughly and re-tune as I did in the video.  Take your time getting the L and LA settings correct.

If backing the L screw out 1/4 turn doesn't improve things, then I'd make sure the engine doesn't have any air leaks (crank seals, impulse line, intake boot, etc.) before messing with the carb any further.


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## MasterMech (Mar 10, 2013)

osagebow said:


> Question for ya Mech - will the spline tool for a MS 290 (I know I'd have to fool with the tabs to get to it) be the same one as a Husky 350?


 
AFAIK - The MS290 uses a standard flat-head screwdriver for carb adjustments.  The only tool required may be the one used to remove the limiter caps on the carb.


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## MasterMech (Mar 10, 2013)

STICK said:


> *I FOUND THIS ADVICE*
> It seems to work well without a tach. But, what do I know, I am just a cowboy with a bag of tools.
> This is routine operator maintenance.
> *1. *Start your saw and run it for a few minutes to warm it up.
> *2. *Set your saw down, let it idle for 30 seconds, and then pick it up and tip it forward (handle up and bar down).


 
The saw should run upright, upside down, standing on-end, or lying on its side equally well. Letting it idle for 30 seconds doesn't really do anything for it either. If the saw stalls or changes rpm when it changes position, the crankshaft bearings/seals are most likely worn and/or leaking and should be replaced. Pressure/vacuum test to confirm.



> *3. *If it keeps running, go to Step 4. If it stalls, tighten the *Low Speed* screw. This will reduce the amount of fuel entering the carburetor. Repeat Step 2 as necessary.


 
No it won't. The L screw only affects the amount of fuel delivered with the throttle closed or partially open.



> *4. *Rev (accelerate) the idling saw.
> *5.* If it accelerates fine, go to Step 6. If it “dogs,” loosen the *Low Speed* screw. This will increase the amount of fuel entering the carburetor. Repeat Step 4 as necessary.


 
Again, incorrect. The inlet needle valve and the diaphragm control fuel flow into the carburetor. This happens automatically and requires no routine adjustment from the operator.



> *6. *Rev the idling saw for about 5 seconds (never rev it for 10 seconds or longer).
> *7. *If it “flutters” while being revved, this is good, so go on to Step 8. If it “screams” while being revved, this is bad. Loosen the *High Speed *screw. Repeat Step 6 as necessary.
> *8. *If the chain is stationary while the saw idles, you’re finished.
> *9. *If the chain rotates around the bar while the saw is idling, adjust the *Idler Screw* as necessary to make it stop. This situation can be fixed in a matter of seconds and is extremely dangerous if not corrected.


 
When setting the final idle rpm's, the L screw is generally set quite rich to prevent the saw from leaning out excessively on decelleration. This is what I'm doing in the video at aprox the 02:10 mark. The L and LA settings should be finalized before moving on to the H setting because the L setting will affect the H setting but not vice-versa.



> That’s it. Less than five minutes of your time can make a big difference in how well your saw runs. Two additional tips are 1) use hot water and dish soap to clean a paper-type air filter (let it dry before using), and 2) use chainsaw gas to clean a wire-type air filter (you don’t need to let it dry before using).
> This information will help your saw run more effectively and efficiently.


 
I totally agree with cleaning the air filter and the muffler screen. Should be done before you begin tuning. Also, you should reset to factory default carb settings (if known) before getting started.


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## HDRock (Mar 11, 2013)

MasterMech said:


> Also, you should reset to factory default carb settings (if known) before getting started.


 
The only factory default settings I can find for the 445 are
  Maximum power speed – 9600 RPM
 Maximum recommended engine speed – 13,000 RPM
Idle speed – 2700 RPM
 If I had a tach , would I be trying to set the high RPM 9600 and not exceed 13,000 ? If not, What do they mean by the maximum power speed ?
 in the manual they don't give you the number of turns to start with, because they don't want you adjusting  the saw,I see most saws are 1 to 1 1/4 out to start


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## MasterMech (Mar 11, 2013)

HDRock said:


> The only factory default settings I can find for the 445 are
> Maximum power speed – 9600 RPM
> Maximum recommended engine speed – 13,000 RPM
> Idle speed – 2700 RPM
> ...


 9000 RPM will be where the saw makes the most power. 

13000 RPM will be what you set the H setting to. 

You can tune so long as you can get the saw started.  A bit easier if it's somewhat close to start with however.


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## pyroholic (Sep 13, 2013)

Are the numbers (rpm) and process for the L and LA settings going to be the same for all Stihl's with the only variants being the max rpm?  If not where is this info at?  specifically looking for specs for the 038 magnum, but need to know for my other saws too.


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## MasterMech (Sep 13, 2013)

pyroholic said:


> Are the numbers (rpm) and process for the L and LA settings going to be the same for all Stihl's with the only variants being the max rpm?  If not where is this info at?  specifically looking for specs for the 038 magnum, but need to know for my other saws too.


The specs are generally in your owners manual.  Your 038 will tune exactly like the 460 in the vid but your factory max rpm is 12500 I believe.  I would tune it by ear first and see where you end up.  If you have it set at 13k or less and it's four-stroking out of the wood, I wouldn't worry about fattening it up to 12500.


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