Lakeside53
Stihl Wrenching
yes - that is optimal mixture (max power) but back it off a little for general use.
14,600 on a 460??
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Cole90
ArboristSite Lurker
I just bought my new 460 today with the dual port muffler cover and tached it at 14,120 after a minor carb adjustment.
Lakeside53
Stihl Wrenching
So.. pull the limiter cap and make it richer... I bet it cuts better at a lower "wot" (terrible way to tune...)..like 13 - 13.5k
With a good oil do you have to worry about it throwing a piston or rod when it's 4strokin? Or should it hold up without demolishing itself as long as I don't get stupid with it of course
I keep hearing the 029 is forged bottom end but,I figured I'd ask before I go and tune my muffler mod.
I keep hearing the 029 is forged bottom end but,I figured I'd ask before I go and tune my muffler mod.
huskystihl
Addicted to ArboristSite
Not doubting the stihl tech here but either the saw is rich or it isn't. How can a saw cut better at 13,500 if it's happy at 14,500? Every saw I have ever owned is a oily slow pig if it gets to much fuel and loses power in the cut. I know theres a line between lean and rich but I don't get people that say it will cut better at 1000 rpms slower when it was tuned perfect before.
"You are exactly right. Factory spec is a ball park number. Nothing replaces fine tuning with timed cuts."
+1
The fastest free rev rpm obtainable will be considerably higher than the "sweet spot" in the power curve at full load.
Some of my saws will easily rev past 14,000rpm's with a relativley lean setting, and still "4-stroke" a bit at no load, or when the load is removed during a cut. They do loose some mid-range power at heavy/full load if set too lean.
My new Husqvarna 435 (strato-charged engine) is a prime example of this. It LOVES to rev, and a lean setting results in high rpm's, but it "pulls" out of the good power curve much easier when working it hard, compared to running it just a tad richer with less no load rpms.
My 268XP is another saw that easily goes past 14,000rpm's. It doesn't seem to care in the cut about the lean setting, but I keep it around 13,700 or so no load rpm's. At that setting, it cuts fine, and instantly 4 strokes in a cut if the load is removed. At leaner settings, at full load it revs a tad to high for my liking before 4 stroking when the load is removed.
It's always best to er slightly on the rich side with these things, especiailly with work saws, unless, as mentioned, you are showing off at a GTG. Another thing to consider, is that a tad more fuel also carries more lubrication to the internals with it, and reduces EGT's........Cliff
+1
The fastest free rev rpm obtainable will be considerably higher than the "sweet spot" in the power curve at full load.
Some of my saws will easily rev past 14,000rpm's with a relativley lean setting, and still "4-stroke" a bit at no load, or when the load is removed during a cut. They do loose some mid-range power at heavy/full load if set too lean.
My new Husqvarna 435 (strato-charged engine) is a prime example of this. It LOVES to rev, and a lean setting results in high rpm's, but it "pulls" out of the good power curve much easier when working it hard, compared to running it just a tad richer with less no load rpms.
My 268XP is another saw that easily goes past 14,000rpm's. It doesn't seem to care in the cut about the lean setting, but I keep it around 13,700 or so no load rpm's. At that setting, it cuts fine, and instantly 4 strokes in a cut if the load is removed. At leaner settings, at full load it revs a tad to high for my liking before 4 stroking when the load is removed.
It's always best to er slightly on the rich side with these things, especiailly with work saws, unless, as mentioned, you are showing off at a GTG. Another thing to consider, is that a tad more fuel also carries more lubrication to the internals with it, and reduces EGT's........Cliff
huskystihl
Addicted to ArboristSite
I just set them rich to the point they don't have power in the cut and then lean them out till they do. I have a tach but it was a waste of money "for me anyways" Maybe thats not the right way since every saw I have bought new from my stihl dealer is crazy rich and unimpressive to say the least, but I have never had one seize. Well, not a stihl or husky anyways. Now my 372 is a different story with those dang rev limiters, I let the dealer set it and see what happens. No failures yet so I guess their dead on.
It's all about how the saw preforms in the CUT.......what the man is saying is that WOT (no load) don't mean sheet.All about powerband and plug color....the rest is just pecker measuring.
huskystihl
Addicted to ArboristSite
I'm pretty sure thats what I was getting at. A tach don't mean squat on a 13,500 saw if it dies in the cut or vise versa.
Tzed250
Addicted to ArboristSite
.
RPM doesn't matter.
Correct mixture does matter.
.
RPM doesn't matter.
Correct mixture does matter.
.
wigglesworth
Booned
Just for those inquiring minds....the saw in question, my MS 460, is now ported and milled. It now holds more RPM in the wood, with the saw tuned at 13.8k than it will at 14.6k. Just thought some would like to know. 
Metals406
Granfodder Runningsaw
Just for those inquiring minds....the saw in question, my MS 460, is now ported and milled. It now holds more RPM in the wood, with the saw tuned at 13.8k than it will at 14.6k. Just thought some would like to know.
Good point, and consistent with what I found with my Pastors 046. . . It would 4 stroke past 14,600 no load, but cut the strongest in the wood set to 13,500 no load. This was right after a muffler mod @ 100% of exhaust area at cylinder wall.
wigglesworth
Booned
Yep, as a matter of fact, I can lean it out to 14.6K now and it still 4 strokes nicely, but lacks the ball's in the wood. My 038 Mag is the same way. Leaned out to 13.5K, she still 4 strokes, but falls on its butt in the wood. Set her down to 12.5K, it doesnt care what you do to it, it just pulls. The funny things is they both sound rich as crap at WOT to me.
This is interesting!
Metals406
Granfodder Runningsaw
:agree2::agree2:
Tzed250
Addicted to ArboristSite
.
It takes fuel to make power.
.
It takes fuel to make power.
.
wigglesworth
Booned
It really takes a sufficient amount of fuel, in PPM in the correct proportions with the incoming air, to make the best power across the engines loaded speed range.
The efficiency of the engine plays a role here (as does the quality of the air it's being mixed with), and the carburetor/intake system may not be a linier curve as far as the A/F ratio goes. Carburetors use the venturi principle to creat a low pressure area to pull fuel from the carb into the throttle bore, and atomize/mix it with the incoming air. The velocity of the incoming air has an impact on the A/F ratio, as it's not possible to keep it at exactly the same ratio clear across the speed/load range. The low speed curcuit feeds some fuel thru transistion and at full throttle as well.
In any case, I suspect this is propably why we can still hear "four stroking" at really high rpm's on some saws, but they act or go slightly lean in the cut at lower rpm's (less incoming air velocity) and hurt torque and mid-range power.
I have quite a few saws that need a slightly richer no load setting, to pull harder in the cut when the engine settles into it's real power curve. I prefer to have them four stroke a bit any time the load is quickly removed anyhow. It got to be better for the engine not going really lean and running extremely high rpm's.....Cliff
The efficiency of the engine plays a role here (as does the quality of the air it's being mixed with), and the carburetor/intake system may not be a linier curve as far as the A/F ratio goes. Carburetors use the venturi principle to creat a low pressure area to pull fuel from the carb into the throttle bore, and atomize/mix it with the incoming air. The velocity of the incoming air has an impact on the A/F ratio, as it's not possible to keep it at exactly the same ratio clear across the speed/load range. The low speed curcuit feeds some fuel thru transistion and at full throttle as well.
In any case, I suspect this is propably why we can still hear "four stroking" at really high rpm's on some saws, but they act or go slightly lean in the cut at lower rpm's (less incoming air velocity) and hurt torque and mid-range power.
I have quite a few saws that need a slightly richer no load setting, to pull harder in the cut when the engine settles into it's real power curve. I prefer to have them four stroke a bit any time the load is quickly removed anyhow. It got to be better for the engine not going really lean and running extremely high rpm's.....Cliff
ShoerFast
Tree Freak
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+1 Gotcha Lake,
The slight burbling out of the wood is fuel that dose not burn with-out the extra cylinder pressure you get in a cut.
most gasoline engines will burn fuel from 11 : 1 to about 17 : 1 (if it has enough spark advance)
That 10 : 1 ~ 11: 1 range might flame out as there is not enough O2 under no load. But two things happen under a load, cylinder pressure/firing-temperature goes up, and the engine slows down.
Slow a WOT carbureted engine down with the same sized throttle opening/carb-size, and you automatically will get a slightly leaner mixture. (less air velocity = less carb - airstream pressure differential)
Put another way, fuel is drawn into the air-stream at WOT and hi-RPM's as the air has a very low pressure.
Lower a WOT engine speed, the air-stream pressure rises slightly and draws less fuel, slightly raising the air-fuel ratio (leaner).
The nutshell behind why timed cuts will give the best 'H' setting of any saw.
After a timed cut "h" setting is established would be a good time to take check the free-speed for a quick reference for future tunes.
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1savagehunter
ArboristSite Operative
Help please
I was by my saw mechanics the other day and he checked the rpm's on my saw (stock 460) he said the RPM's were to fast at 12400 and turned it back to 11900. I was chocked at him but took it home and cut into some big stuff. I could tell that the RPM's were slower but I found that the saw had more power. Call me stupid but I don't get this ... I understand that the saw is running richer so it is using more fuel (power) but I don't get the trade off power vs. RPM's. I would like someone to explain this to me. I went back to talk to my mechanic to have him tell me that he knew the saw was running to lean when I came in as the muffler was not black and oily. I'm not looking for a hot saw speed but I don't want to be running a saw that could perform safely at a higher speed. I'm using this saw semi-professionally and up to know have relied on the mechanic but have decided after this last go around to try to gain abit more knowledge. I guess I would like to know how to adjust the saw for optimal cutting performance without scoring a piston. Thanks for any help any of you could provide.
I was by my saw mechanics the other day and he checked the rpm's on my saw (stock 460) he said the RPM's were to fast at 12400 and turned it back to 11900. I was chocked at him but took it home and cut into some big stuff. I could tell that the RPM's were slower but I found that the saw had more power. Call me stupid but I don't get this ... I understand that the saw is running richer so it is using more fuel (power) but I don't get the trade off power vs. RPM's. I would like someone to explain this to me. I went back to talk to my mechanic to have him tell me that he knew the saw was running to lean when I came in as the muffler was not black and oily. I'm not looking for a hot saw speed but I don't want to be running a saw that could perform safely at a higher speed. I'm using this saw semi-professionally and up to know have relied on the mechanic but have decided after this last go around to try to gain abit more knowledge. I guess I would like to know how to adjust the saw for optimal cutting performance without scoring a piston. Thanks for any help any of you could provide.
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