The official saw tuning thread.

[046]

tune my carbs quite similar to gypo's method.

1. low range is controlled by a combo of butterfly opening size and low speed mixture.

2. high range screw only control high range.

once you realize what controls what, adjusting is easy.

always start H & L adjustment, from factory recommended settings. lightly bottom adjustment screws, then back out one turn, 3/4 turn or what ever mfg recommends.

unscrew butterfly adjustment until completely closed. then screw in 1/2 turn open. start your low end mixture adjustment with butterfly just barely open. (if butterfly is opened too far, you cannot adjust low mixture properly)

start saw and blip throttle lightly... saw will want to die from butterfly almost closed. after warming up for 1-2 minutes. then open up butterfly screw just barely enough to get saw to idle.

then adjust your L screw in or out until you find a peak at which saw runs at highest rpm. this will usually be within 1/2 turn of factory starting position. then go back and adjust idle to just below engaging clutch.

if you cannot find a peak rpm point... something is wrong. either an air leak or a blocked L circuit.

assuming you've successfully adjusted the low range. then you are ready to do H range.

with bar/chain, air filter as you intend to operate. run saw wide open for a few seconds to see if saw blubs on high end. if you don't have a tach. objective is for saw to start blubb wide open. limiting rpm.

with a tach hooked up, adjust H screw to factory recommended settings. and you are done.... note instructions for H setting is for a stock saw. use gypo's instructions below for mod saws.

leaner the setting, faster and more power saw will run. but higher risk of too lean and burning up piston. it's much safer to run saw slightly rich, then slightly lean.

hope this helps to clarify adjusting your carb...

I think carb adj. is where alot of people go wrong with a saw.
I know some local loggers who equate out of wood rpm with power, however, fuel requirements are alot different in the wood than out.
They were always going for max rpm out of the wood and wondered why they were losing bottom ends out of 088's and 066's.
Over the years I have developed my own method of carb adjustment.
Given that the carb has good diaphrams and the filtre is clean, I first turn up the idle speed screw (LA) till the chain begins to turn, then I turn in or out the L to get the highest idle rpm where the chain is turning the fastest, then I turn out the L about 5 minutes or so. If the saw then responds fast to full throttle I leave it there and turn out the LA till the chain just stops turning.
Then I go to the H and find the highest audible rpm and then richen it out about 5 minutes till it's not a flat out scream, but a slight burble.
This procedure I repeat at least two times till I get it right. Don't forget the 32:1.

John

 

[Haywire Haywood]

with a tach hooked up, adjust H screw to factory recommended settings. and you are done....

That's what I've been doing for the high end, but get the feeling that I'm not really "tuning" the saw because I've heard Andy and others say many times that every saw is different and what it's tuned at is +/- 1000 rpms from the factory spec for the high end. I'd hate to think I was running lean and risking disaster or rich and not getting all the potential power available to me.

I'll have to give your low end technique a try tho, I may have had my LA screw holding the butterfly too far open on the 346.

Ian

 

[Lakeside53]

tune my carbs quite similar to gypo's method.

.

then adjust your L screw in or out until you find a peak at which saw runs at highest rpm. this will usually be within 1/2 turn of factory starting position. then go back and adjust idle to just below engaging clutch.

if you cannot find a peak rpm point... something is wrong. either an air leak or a blocked L circuit.

...

Good post 046, but...

Did you mean to say this? Setting L to peak will be way too lean on most saws, make for hard starting and poor acceleration.

Most saws, you'll find L peak then back it off about 1/4 turn i.e. firmly on the rich side, but still idling nicely, then adjust LA to compensate. Test for too rich by idling for a few minutes then tip the saw forward and see it it coughs out for stumbles badly -a sign of gas pooling. If so tweak L maybe a slight amount leaner and test for acceleration response.

 

[Lakeside53]

So............. My 084 with 30" bar @ 12,500 that sounds too rich to me? (non rev limited coil) I'm chicken to go any faster.......... I'm at about 1000 feet.

Bought the stihl edt 8 a few months ago.

12,500 is max. I'd leave it just where it is... Max rpm is important on that big saw to allow for sufficient lube to the big end.

 

[046]

opsss.. should have posted my instructions for H setting is for a stock saw. follow gypo's instructions above for a modded saw..

That's what I've been doing for the high end, but get the feeling that I'm not really "tuning" the saw because I've heard Andy and others say many times that every saw is different and what it's tuned at is +/- 1000 rpms from the factory spec for the high end. I'd hate to think I was running lean and risking disaster or rich and not getting all the potential power available to me.

I'll have to give your low end technique a try tho, I may have had my LA screw holding the butterfly too far open on the 346.

Ian

 

[046]

thanks for pointing that out. usually end up richening up a but further to help response. mainly wanted to point out proper L adjustment is not possible with butterfly opened too far.

Good post 046, but...

Did you mean to say this? Setting L to peak will be way too lean on most saws, make for hard starting and poor acceleration.

Most saws, you'll find L peak then back it off about 1/4 turn i.e. firmly on the rich side, but still idling nicely, then adjust LA to compensate. Test for too rich by idling for a few minutes then tip the saw forward and see it it coughs out for stumbles badly -a sign of gas pooling. If so tweak L maybe a slight amount leaner and test for acceleration response.

 

[Lakeside53]

Yes, you can't tune with an excessive LA.

I normally reset the L to factory (say - 1 turn out), wind in the LA a good amount, start the saw, back off the LA until it idles reasonably, then check the L for range (plus/mnus 1/4 turn) and set it to a good but slightly rich idle, then LA again so the chain stop running. If it won't at a decent idle speed, change the clutch springs.

Why? I can't see or feel the LA engage the throttle or the postion of the butterfly on 99% of the saws I tune..

 

[ShoerFast]

Nope... I'm useless tuning a stock muffler 361 without a tach. NO real burble at all.

Unless the muffler has been gutted on the inside, cutting the exit hole will have zero effect on the muffler output.. It's fed though a long tiny tube... unless you actually cut that tube away too, and that will negate your spark arrester. I add a second 16mm port and leave the factory port alone. Maybe I'm confused with what you did.


I assume you looked at this thread showing the muffler internals?

http://arboristsite.com/showthread.php?t=33528

Thanks Andy

I need to go back in there, I widened existing hole, If there is any way that I can still use the factory spark arrestor, and free up some exhaust, it is so dry here much of the year. Understanding I may just have to add an extra port/screen.

If I can free up enough 361 exhaust, will the burble become evident?

 

[Lakeside53]

Thanks Andy

I need to go back in there, I widened existing hole, If there is any way that I can still use the factory spark arrestor, and free up some exhaust, it is so dry here much of the year. Understanding I may just have to add an extra port/screen.

If I can free up enough 361 exhaust, will the burble become evident?

Yes.. somewhat...


I'd leave the existing hole alone and add the aux hole like I did, with screen. There no real way to use the factory screen and make any material improvement in flow.

 

[ShoerFast]

Yes.. somewhat...


I'd leave the existing hole alone and add the aux hole like I did, with screen. There no real way to use the factory screen and make any material improvement in flow.

I got it apart now*, Yes!

When I did it when I first got it home, I was going to cut the very next day and did something quick. Well it is still snowing and I have some 16mm chromed certified LMH tube (Lawn Mower Handle) .

Thanks Again Andy, I saw the PN for the blower screen, it will be green here for another few weeks, but turns brown and crackly, scary with out a screen.

We all are deeply indebted to your dedication!

* I have a horseshoeing tool that gets in there and pulls the creased-seam up very easily! I would not get one to just do mufflers, even if I did a lot of them. But something like this from a Flea Market would be worth tossing in a tool box.

This link has a close-up view of the tip: http://www.stcroixforge.com/products/handtools/nailpuller.html

 

[stihl 440]

idle

I think carb adj. is where alot of people go wrong with a saw.
I know some local loggers who equate out of wood rpm with power, however, fuel requirements are alot different in the wood than out.
They were always going for max rpm out of the wood and wondered why they were losing bottom ends out of 088's and 066's.
Over the years I have developed my own method of carb adjustment.
Given that the carb has good diaphrams and the filtre is clean, I first turn up the idle speed screw (LA) till the chain begins to turn, then I turn in or out the L to get the highest idle rpm where the chain is turning the fastest, then I turn out the L about 5 minutes or so. If the saw then responds fast to full throttle I leave it there and turn out the LA till the chain just stops turning.
Then I go to the H and find the highest audible rpm and then richen it out about 5 minutes till it's not a flat out scream, but a slight burble.
This procedure I repeat at least two times till I get it right. Don't forget the 32:1.

John

Gypo, I used your method of tuning the idle and I tuned the idle on my 280 because the chain was running at idle and it worked perfectly. She purrs like a kitten now, thanks. I'm still out of bullets for you . :rockn: :hmm3grin2orange:

 

[Haywire Haywood]

I got him for ya.

Ian

 

[Dan Forsh]

That's my problem, I hear no burble, no 4 stroking. All I hear is WAAAAAAAAA when I hold the trigger down. Madsen's audio doesn't help either, it just sounds like a wide open chainsaw to me. Frustrating it is.

Ian

Yep, that's EXACTLY my sentiment. I bought a tach too.

But I'm going to keep reading this thread, the best one I've seen for a while.

 

[stihl 440]

thanks.

I got him for ya.

Ian

Thanks for getting him for me!

 

[Haywire Haywood]

I re-tuned the low end just now and it's idling much better than before. I reset the jets to 1 turn out and started it, let it warm up (had to keep bumping the throttle to keep it running). I then turned the LA in till the chain would turn and with the tach clamped to the plug wire, adjusted the L till I got the highest rpm. I then richened it about 1/4-1/3 of a turn and reset the LA to about 3k. The chain stopped turning at about 3500 IIRC. We'll see how it starts cold. It restarted on the first pull but it was good and warm by then.

High end? I just made sure it was about 200 under factory spec. Better safe than sorry I suppose. Maybe the GTG can edumacate this :monkey: on burble.

Ian

 

[Stihl_Learning]

Yep, that's EXACTLY my sentiment. I bought a tach too.

But I'm going to keep reading this thread, the best one I've seen for a while.

my tach didn't come in Friday
but should be here monday

I liked the thread so well I copied and pasted it into Word so I could print it out as a reference guide to keep with the Tach

but now I gotta keep watchin it for changes opcorn: opcorn: opcorn:
John

 

[PA Plumber]

Good Thread.

Is the one turn out for "L" and "H" pretty commom across the board for Stihl saws? What about the "LA" screw? Is the factory "LA" adjustment also one turn out?

 

[Haywire Haywood]

The workshop manual told me what the initial settings for the H and L were, but didn't mention a standard setting for the LA (it's actually "T" on my Husky).

Ian

 

[PA Plumber]

The workshop manual told me what the initial settings for the H and L were, but didn't mention a standard setting for the LA (it's actually "T" on my Husky).

Ian

It's "T" on my small Echo also. "LA" on the Stihl.

 

[ShoerFast]

Ms-361

The 361 seems an odd duck to me. My ear just dose not tell me what I would like to know.

Factory new, they want it to do it's dirty work via a 9MM hole in the internal exhaust plumbing. That dog wont hunt for me, so in the existing exhaust outlet area, I welded a tube with an 5/8" ID . (Andy, I really like your 361 muff mod, but would like to keep the smoke a little further from the wood and punk-bark here)

With a 5/8 tube for an exit , to me, the 361 still dose not seem to have a good burble when set too rich, so I did some timed cuts.

Starting way fat , you could tell that it just did not even seem like it could get out of it's own way.

1 1/4 turns out from all the way in, cutting a 16" Douglas Fir.....

1 1/4 @ 18 mississippi's

1 1/16 @ 16 mississippi's

1 1\16 @ 14 mississippi's

1 turn out, seemed a good 12 mississippi's and a nice transition from free speed into the cut .

At 7/8 and 3/4 turn out , it seemed that there was way too much "Whhhhhhhhh" and fell on its face in the cut, didn't complete the cut, but it would not have made the half way point in 8 mississippi's, and you could tell that it was slower cutting then even the 1 1/4 turns out.