RPM info needed

[toyotaracer9]

I am in need of rpm numbers for a stihl 039 and a husqvarna 359 , both without the bar and the 359 has the muffler modded . thanks for the help .

and if someone could please give me the reason some people tach with and some without the bar ???

 

[ol'homey]

I called the Stihl 800 tech number a while back and asked them the proper way to set the hi speed mixture on their saws. Here's what I remember:
1. saw is at operating temp with fresh mix and clean filter
2. bar and chain removed
3. turn out screw so mix is rich and saw is blubbering
4. slowly turn screw in until you get to the rpm spec
5. adjust idle mix for best idle with no hesitation on acceleration
6. recheck max rpm and adjust to spec if needed

If a bar is installed you will have to turn the hi speed screw in further to achieve the max rpm spec. This results in a lean mixture. Folks that don't understand this and set the saw to max rpm with a big bar installed will have a leaned out saw that will sound great but will be purchasing a new jug and piston kit sooner rather than later. FWIW the above is what I remember from talking to a Stihl tech and could be totally wrong, as I know most people leave the bar on and have many reasons why they do this. One I've heard is "the saw will over rev and blow up if I try to set max rpm without a load!" If you back out the hi speed screw so the saw is blubbering the saw isn't going to over rev. Then you just turn the screw in until you hit the rpm spec.

 

[Dan Forsh]

I called the Stihl 800 tech number a while back and asked them the proper way to set the hi speed mixture on their saws. Here's what I remember:
1. saw is at operating temp with fresh mix and clean filter
2. bar and chain removed
3. turn out screw so mix is rich and saw is blubbering
4. slowly turn screw in until you get to the rpm spec
5. adjust idle mix for best idle with no hesitation on acceleration
6. recheck max rpm and adjust to spec if needed

If a bar is installed you will have to turn the hi speed screw in further to achieve the max rpm spec. This results in a lean mixture. Folks that don't understand this and set the saw to max rpm with a big bar installed will have a leaned out saw that will sound great but will be purchasing a new jug and piston kit sooner rather than later. FWIW the above is what I remember from talking to a Stihl tech and could be totally wrong, as I know most people leave the bar on and have many reasons why they do this. One I've heard is "the saw will over rev and blow up if I try to set max rpm without a load!" If you back out the hi speed screw so the saw is blubbering the saw isn't going to over rev. Then you just turn the screw in until you hit the rpm spec.

Quite a few bits of vital information missing here. How exactly do you know when you've hit the rpm spec? Are you assuming that everyone has a tach to hand?

 

[ol'homey]

Sorry here's the missing info:
1. you get a service manual or call the Stihl tech line to obtain the max rpm spec for your model.
2. you obtain a Stihl tiny tach or other tachometer to measure rpms so that you know when you are at the spec.

You must have a tach and the max rpm spec for your model before you can begin this procedure. Hope this helps.

 

[toyotaracer9]

thanks for the info so far , yes I do have a tach and everything ready to be tested . I am hoping someone will chime in with the RPM specs .

 

[Canyon Angler]

My stepfather had this funky German tach which sensed vibrations etc., and didn't need to count spark cycles, no wires or anything, you just set it on the engine and it would tell you rpm. I wonder whether something like that would work? (Not sure it went to 13,OOO RPM though!)

 

[Urbicide]

On the 359, max RPM's out of the cut with bar and chain installed is 13,500. I don't know how you could properly set your carb without the load of the chain on it. Hope this helps.

 

[Lakeside53]

All Stilh WOT specs are with the bar and chain INSTALLED... and correctly tensioned.

 

[ol'homey]

OK, let's say I have an 044 Stihl and 2 bar/chain/sprocket combos. The first one is .325 chain/7T sprocket and the smallest bar that will fit the 044. I hand you the saw and tell you to set the carb to the max rpm spec. I take a sharpie and mark where you set the high speed screw. Then I put a .404 chain/8T sprocket and the longest Stihl bar that will fit the 044. I hand you the saw and you set it to the max. rpm spec again. I look at the mark I made and notice the screw is set leaner than before. There can only be one correct max rpm carb setting. Which one is right?
Then I take the bar and chain off and have you set the max rpm again just for the heck of since it's not the proper way to do it. I notice that the screw is now set richer than either of the above marks. Then I look on the wall and see a monster 60" bar that fits and we give that a try, but you can't get the saw to hit the max rpm spec no matter how far you lean it out. Looking at the marks we're half a turn leaner than the no load mark and still can't hit the max rpm. What's going on? Too much load from the bar? What do we do now? I've got high speed screw marks all over the place (no bar, short bar, long bar, extra long bar). Are any of them right? Does the max rpm spec only apply to a specific bar/chain/sprocket combo for each model saw?

 

[ol'homey]

http://www.madsens1.com/sawtune.htm
(8) Set the high speed fuel adjustment. Hold the trigger wide open and check the RPM with the tachometer. The listing below identifies the maximum RPM setting for popular pro saws without bar & chain:


STIHL 044 - 13,500 RPM
STIHL 066 - 13,000 RPM
STIHL 084 - 11,500 RPM


HUSQVARNA 272 - 13,500 RPM
HUSQVARNA 288 - 13,000 RPM
HUSQVARNA 394 - 13,000 RPM
HUSQVARNA 3120 - 11,500 RPM
NOTE: If you do not have a tachometer, set the RPM level so that the saw "four cycles" or "blubbers" at wide open throttle. Do not attempt to set at maximum RPM levels without a tachometer. Setting the adjustment slightly rich will diminish performance, but reduce the possibility of damage to the saw engine.

Do you see above where it says "without bar and chain"?
Somebody needs to call Madsen's and tell them they don't know what they're doing before they screw up any more saws! No bar and chain! What are they smoking? Oh the horror......LOL!

 

[Lakeside53]

Masdens has that info forever. Stihl says with bar and chain. Do whatever you want, but the bar and chain make a big difference. Masdens method will leave your saw set "conservatively". Not so bad... if you like it "that conservative"

 

[Lakeside53]

OK, let's say I have an 044 Stihl and 2 bar/chain/sprocket combos. The first one is .325 chain/7T sprocket and the smallest bar that will fit the 044. I hand you the saw and tell you to set the carb to the max rpm spec. I take a sharpie and mark where you set the high speed screw. Then I put a .404 chain/8T sprocket and the longest Stihl bar that will fit the 044. I hand you the saw and you set it to the max. rpm spec again. I look at the mark I made and notice the screw is set leaner than before. There can only be one correct max rpm carb setting. Which one is right?
Then I take the bar and chain off and have you set the max rpm again just for the heck of since it's not the proper way to do it. I notice that the screw is now set richer than either of the above marks. Then I look on the wall and see a monster 60" bar that fits and we give that a try, but you can't get the saw to hit the max rpm spec no matter how far you lean it out. Looking at the marks we're half a turn leaner than the no load mark and still can't hit the max rpm. What's going on? Too much load from the bar? What do we do now? I've got high speed screw marks all over the place (no bar, short bar, long bar, extra long bar). Are any of them right? Does the max rpm spec only apply to a specific bar/chain/sprocket combo for each model saw?

Bar and chain combos make a difference, but it's usually a fraction of turn. There is not one perfect setting unless you are in the wood and under load. Anything else is a rough guide. Two things at play - correct mixture and max rpm (i.e. - DON'T EXCEED). They don't have to mean the same thing, and you don't have to set the saw to MAX WOT to have it cut faster ....

Tuning for correct mixture is as much an art as a science. Just tune it for the typical mid-size bar you use and put it at a reasonable setting. If you use the Masdens "wot" without bar and chain, it will be conservative (low when you put one on). If you chase your mixture trying for a the perfect WOT settings, then you will ultimately have problems - always set it a little lower - i.e. - stay way from the edge. I typically run 300-500 lower than max.

 

[ol'homey]

I bet if you mark your setting when you tune for 300-500 rpm below max spec with an avg bar and then take the bar off and tune for the max spec, you will find the settings are pretty close. I would just leave the bar off since it eliminates quite a few variables and will leave you with a conservative mixture. I've seen too many guys run their saw up to max rpm with the bar on and a dirty air filter. Then they eventually change the filter or maybe run the saw out gas a couple of times. Then uh oh they're crying about a scored piston and wondering what could have possibly caused it? The max rpm was right on the spec so it couldn't have been lean right? Wrong! It was lean to begin with, then they changed the filter which leaned it out further. Then they let a saw that was already way lean run out of gas. Recipe for disaster. You set the saw up like Madsen's does and the saw has a better chance of surviving these mistakes.

 

[Haywire Haywood]

In the carb adjustment area of the 346XP shop manual there is a warning section highlighted.

"WARNING! Guide bar, chain and clutch cover must be installed before the saw is started, otherwise the clutch may fly off and cause injury"

I guess you have to start it to adjust the carb, so there ya go from the Husky side of the house.

Ian

 

[Monkeyhanger]

My stepfather had this funky German tach which sensed vibrations etc., and didn't need to count spark cycles, no wires or anything...

Hi,

you got it a little wrong there, those funky German tachs detect the strong electro-magnetic field that the ignition cable produces. They count the sparks not vibrations!

I'm looking at getting one myself but they are quite expensive.

Bye

 

[PetrolHead]

they have some real weird ones out there.
http://www.machovec.com/quest/vibratach.htm

 

[josgmctk]

not weird

this is the tach that Briggs supplies to their shops. the instructions are for any engine up to 50,000 rpm

 

[Monkeyhanger]

they have some real weird ones out there.
http://www.machovec.com/quest/vibratach.htm

Hi,

that is weird...

still I wouldn't trust such a Vibra-tach further than I could spit an elephant.

Bye

 

[sawinredneck]

Hi,

that is weird...

still I wouldn't trust such a Vibra-tach further than I could spit an elephant.

Bye

I have used them, would like to get one, thanks fo the link, they are VERY VERY acurate.. I was using my Mac mutimeter with an inductive pickup for comparison.
Andy

 

[Lakeside53]

Tuning...

Back to tuning... some of this I said last night, but it's just repeated for clarity.

Irrespective of the length of a bar there is only one correct mixture (for given atmospherics and assuming a clean filter).

I doesn't matter whether you are tuning , for example, a blower or a saw. The problem is that a blower is always under full load when you are setting the top end, and a saw is very difficult to tune under full load. It's possible to get a very good tune with a blower; with the the saw it's just an approximation when using the WOT method.

A blower like a BR 420 puts out a little more hp than say an 026. You tune it by peaking the rpm (it's under full load remember...) from the rich side, then backing off about 75 to 100 rpm. The peak in this case is usually about 7600 to 7700 rpm with a decent motor and clean filter.

If you put a saw under load, say with an air wheel, dyno or whatever, you can do the same thing. Peak it, back it off. Not very practical unless you are racing though... You can do timed cuts with a saw, but your technique, chains and wood need to be consistent.

Airplane motor mixture is set the same way for varying altitudes - lean it out to peak EGT (exhaust gas temperature), then back off the recommended amount (like 25 degrees). This method would also work for 2 strokes under load, but I don't know the parameters.

If you have an UNMODIFIED saw, and it's in reasonable shape, the correct mixture is very close to the standard carb settings. The carb needles (sometimes other parts) are calibrated to provide this setting to take the guesswork out of mixture setting. In most cases, this is 1 turn out from gently seated. Generally, at 1 turn out it's slightly rich. When shipped from the factory it's close to this point, but set correctly for power and emissions. Doesn't matter what bar or chain you are putting on - the mixture is correct. The only issue to be concerned about is whether you exceed WOT by UNDER bar-ing the saw.

Chasing the WOT as a method to set the correct mixture is fraught with problems. If your saw end up set more then a 1/8 to 1/4 turn from "standard", find out why... you may be compensating for some other problem that will not remain static over time.

If you've modified your saw, including the muffler, you need to figure out your own "standard" carb settings...