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Author Topic: AT fuel mix  (Read 2616 times)

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Offline HolmenTree

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Re: AT fuel mix
« Reply #20 on: October 02, 2018, 01:24:51 PM »
Let the AT saws when hot idle for a minute before shutting them off.

I see the need for the next advancement in AutoTune and MTronic technology.... is a low fuel warning signal of some sorts.  ;)
Got my first computer MTronic saw in July.  A Stihl 201T for climbing as the old one was worn out.  Did not want to go that way but no real choice anymore as that is all there is out there.
Your low fuel warning comment triggered a thought.
Why do you say that? Specifically.
I think I know...... but would like to hear it from you with your experience.
Ok, we're on the same page about letting a working engine idle some before shutting it off. :)
Low fuel warning on a ATune or MTronic is a no brainer after running one of these saws hard in the wood and then it stops abruptly from running out of fuel. 
The high  heat sink soaks in while you're refuelling and then when you go to start it with the choke on to get the fuel back into the carb(I even tried no choke only fast idle) it dumps extra fuel into the cylinder for protection from the high heat it is sensing. Flooded and lots of cursing to get it going again.
Was a time you had  a little warning when the saw needed to be refueled. These micro processors adjust right to the last drop with nothing to spare to let them cool down at idle.
My MS261CM does offer a short lean warning but easy to miss, 562XP not so good.
Making a living with a saw since age 16.

Offline pine

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Re: AT fuel mix
« Reply #21 on: October 02, 2018, 02:23:16 PM »
Got my first computer MTronic saw in July.  A Stihl 201T for climbing as the old one was worn out.  Did not want to go that way but no real choice anymore as that is all there is out there.
Your low fuel warning comment triggered a thought.
Why do you say that? Specifically.
I think I know...... but would like to hear it from you with your experience.
Ok, we're on the same page about letting a working engine idle some before shutting it off. :)
Low fuel warning on a ATune or MTronic is a no brainer after running one of these saws hard in the wood and then it stops abruptly from running out of fuel.
The high  heat sink soaks in while you're refuelling and then when you go to start it with the choke on to get the fuel back into the carb(I even tried no choke only fast idle) it dumps extra fuel into the cylinder for protection from the high heat it is sensing. Flooded and lots of cursing to get it going again.
Was a time you had  a little warning when the saw needed to be refueled. These micro processors adjust right to the last drop with nothing to spare to let them cool down at idle.
My MS261CM does offer a short lean warning but easy to miss, 562XP not so good.
Ok not where I thought you were going to go with that.  More below on my thoughts.
Absolutely agree about the cool down issue.  I have been very meticulous for years about letting my saws get a cool down after a hard run before shutting down.  You are right, my brush cutters (FS450/550) I can switch the choke to rich and get them to run a little bit longer for a cool down but the chain saws (at least mine) not so easy.  At least you can hear the RPM's increase as they start to run lean so you get a little warning that the tank is going dry.
The issue with the 201T is that of the five 201T that have been sold out of my local dealer in the last 3 months, 3 have had issues ranging from annoying to failure to run.  The technician replaced the carbs on two of them and the problem went away---- for a while.  Now one of those has returned and basically won't run at all.  Two of the 5 have had no issues at all reported by the users.  
Mine has been intermittent.  Initially it would die around 50% of the time on idle down after a WOT run. After break-in was complete and I started to run the saw much harder the issue was reduced to dieing maybe 10% of the time.
I know the computer "learns" as time goes on (according to the tech) and if different users use it inconsistently then the computer has problems with basically being confused.
After checking with one specific Stihl rep, Stihl claimed that it was a fuel solenoid issue and that the carb did not need to be replaced just  the tiny little solenoid.  That was done to mine.  The next hour the saw ran great no issue. Problem resolved  -- or so I thought.  
As the fuel started to run out I heard the RPM increase as it went lean (yes the computer should compensate but I could still hear it just like with my other saws)  I may have let it go a little too long but it did not die in the cut.  After refueling the saw ran great in the cut but went back to the previous issue with dieing at idle as the RPM decreased or if it sat and idled for more than a couple of seconds.
I was hoping that your comment was going to say that there was evidence that the computer got confused/screwed up if it was run out of fuel thus making it run bad due to computer issues.  Thus never to run it out of fuel to avoid fouling up the computer on these new saws.  Back to the drawing board on our issue.

Offline HolmenTree

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Re: AT fuel mix
« Reply #22 on: October 02, 2018, 06:47:35 PM »
There's a  reason why these saws have transparent tanks to view the fuel level.
But easier said then done though when a guy is cutting in the thick of things.
Can't offer any advice on your MS201 besides there has to be a software update for it.
In my mechanical way of thinking a poor idle dropping off to dieing tells me the spark plug electrode gap is getting too wide.
Making a living with a saw since age 16.

Offline realzed

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Re: AT fuel mix
« Reply #23 on: October 02, 2018, 07:50:02 PM »
"Was a time you had  a little warning when the saw needed to be refueled. These micro processors adjust right to the last drop with nothing to spare to let them cool down at idle."
Boy can I relate to that! The first time I ran out with my new 261CM - I had no idea what happened.. it was like someone reached in under my arm and flipped off the kill switch it quit so abruptly.  No stumble - no lean elevated rpm that I noticed - no cough or fart.. just flat quit - 'BANG'..
I had been cutting firewood a lot longer than my 290 would ever have gone on a tank of fuel and I really should have taken note of that fact and figured the tank should be getting down considering how much I had done with it - but in the heat of things it passed me by.
It did start back up after a quick refill, certainly a lot better than I expected after hearing some stories of how hard the M-Tronic deals could be to get back after running out though, which was good!
It really is an amazing little saw - overall I am stlhl (pun intended) impressed every time I fire it up!  

Offline HolmenTree

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Re: AT fuel mix
« Reply #24 on: October 02, 2018, 08:53:41 PM »
Yes knock on wood my new MS261 has been flawless too except once when it was working hard on a hot day in the upper '90s and ran out of fuel.
After refuelling I had to pull the rope about 5 times while holding the throttle wide open and it fired right up.

No big deal, I just thought it was saying to me "Take it easy! It's almost  100 F out here!"
:D

My 562XP wouldn't even have bothered to please me in that heat.
It wouldn't have bothered to run in the first place :D

:)  
Making a living with a saw since age 16.

Offline Al_Smith

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Re: AT fuel mix
« Reply #25 on: October 06, 2018, 05:40:45 AM »
Oh my goodness I go out of town for a few days and somebody resurrects the oil wars .I nearly missed it . :(

Offline ZeroJunk

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Re: AT fuel mix
« Reply #26 on: October 07, 2018, 07:38:19 PM »
The Stihl rep said that HP Ultra would work fine at 70 to 1 . The reason there is no consensus on oil mixes is because anywhere from probably 10 to 1 with an occasional fouled plug and 70 to 1 with good oil and it really doesn't make a flip.

So, you run 32 to 1 and everything works great and you swear that 32 to 1 is the obvious best choice.

And, of course ignore the fact that anything else within reason and you wouldn't have had any problems either.

Offline HolmenTree

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Re: AT fuel mix
« Reply #27 on: October 08, 2018, 08:45:26 AM »
There is still a 32:1 mix ratio on the chart of the Stihl Ultra mix bottle label.
Making a living with a saw since age 16.

Offline Al_Smith

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Re: AT fuel mix
« Reply #28 on: October 08, 2018, 10:34:33 AM »
There is still a 32:1 mix ratio on the chart of the Stihl Ultra mix bottle label.
See I told you.If Stihl thinks it's a valid option and it's on the internet it must be true .They don't think that less is more why should anybody else ?
The great never ending oil debate or war whatever the case.Gotta love it 8)

Offline ZeroJunk

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Re: AT fuel mix
« Reply #29 on: October 08, 2018, 06:19:20 PM »
Why would anybody selling oil advertise that less will do the job. Other than Amsoil, who knows about them.
Why would anybody selling saws suggest anything that would cause them problems.

I suspect Stihl and Husqvarna have tested every way imaginable and if there was anything to running more than 50 to 1 they would be all over it.

But, people are perfectly capable of believing anything.

Offline trapper

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Re: AT fuel mix
« Reply #30 on: October 08, 2018, 07:28:08 PM »
Went to get saw gas today.  Putting oil in the can I spilled a fair amount.  Didnt know just how much i spilled but I know less than half.  I added 1 gallon of gas.  I then added the proper amount of oil for 2 gallon at 50 to 1 to another can put in 2 gallons of gas and mixed the 2 cans together and should result in a slightly heavy mix.
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Offline Southside logger

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Re: AT fuel mix
« Reply #31 on: October 08, 2018, 07:32:13 PM »

Why would anybody selling saws suggest anything that would cause them problems.


The EPA. 
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Offline Al_Smith

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Re: AT fuel mix
« Reply #32 on: October 08, 2018, 07:51:42 PM »
The less is more thing goes like this .For reasons unknown some have suggested that heavier oil mixes lean out the fuel to air ratio causing a lean burn .The fuel to air mixture always had been controlled by the carb .Maybe somebody rewrote the book of physics and didn't tell me about it .
Where this idea that heavier mix ratios caused carbon build came from I really don't know .The old boat motors used 30WT oil mix at 16 to 1 and the only time they carbon fouled was running slightly above idle at trolling speeds .Even then you pull your lines and open it up.In about 5 minutes good as new .

Online bandmiller2

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Re: AT fuel mix
« Reply #33 on: October 08, 2018, 07:53:52 PM »
I have mentioned this years ago. I was the mechanic for a medium sized fire dept. We would keep a can of mix and a can of straight gas on the trucks. When they weren't looking I would mix 100/1 Amsoil in the straight gas can so if they  dumped the pure gas in a saw no harm. We had some old two cycle Homelite pumps that called for a real rich mixture of oil something like 10/1. When they would take them out pumping I would give them a couple of plugs and a wrench, they would smoke and puke out the exhaust. I got fed up and put 50/1 in the tank kinda expecting to get some new pumps. The old homies thought it was ice cream they perked up and never ran better and are probably still running. Frank C.
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Offline Al_Smith

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Re: AT fuel mix
« Reply #34 on: October 08, 2018, 08:04:00 PM »
Look at it like this .Those old Homies running 10 to 1 could substitute as mosquito foggers while moving water therefore doing double duty in a way .You're probably right about still running some of that old stuff was designed to run forever .

Offline John Mc

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Re: AT fuel mix
« Reply #35 on: October 08, 2018, 09:52:26 PM »
The less is more thing goes like this .For reasons unknown some have suggested that heavier oil mixes lean out the fuel to air ratio causing a lean burn .The fuel to air mixture always had been controlled by the carb .Maybe somebody rewrote the book of physics and didn't tell me about it .
Where this idea that heavier mix ratios caused carbon build came from I really don't know .The old boat motors used 30WT oil mix at 16 to 1 and the only time they carbon fouled was running slightly above idle at trolling speeds .Even then you pull your lines and open it up.In about 5 minutes good as new .
The only time I've ever heard anyone make that argument was in the context of trying to convince someone to tune their saw to the fuel they are actually using, and if they switched fuel (whether changing the fuel/oil mix or changing from ethanol to non-ethanol gas), to consider adjusting their carb to match.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

Offline ZeroJunk

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Re: AT fuel mix
« Reply #36 on: October 09, 2018, 02:43:44 PM »
Some boat motors used plugs that did not have an over lapping electrode, just arced to the sides. I had one. A Force something or the other. And, they stayed fouled even at 50 to 1 .  I replaced them with a standard type plug and had no more problems. Didn't see any difference in performance and they didn't poke a hole in the piston. so, all good.

Offline barbender

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Re: AT fuel mix
« Reply #37 on: October 09, 2018, 05:36:21 PM »
I have a 40 horse Mercury that uses the same style plug. I don't believe I ever fouled one. I did have an electrode fall off in my saw and destroy my p&c in short order, because the saw kept running. The plug was functioning just like those outboard plugs👎
Too many irons in the fire

Offline hamish

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Re: AT fuel mix
« Reply #38 on: October 09, 2018, 09:24:39 PM »
The less is more thing goes like this .For reasons unknown some have suggested that heavier oil mixes lean out the fuel to air ratio causing a lean burn .The fuel to air mixture always had been controlled by the carb .
True however most have missed the part in the book that tells that a richer fuel/oil mix results in a leaner fuel/oil mix, thus reducing the available fuel/oil mix for cooling and performance...........unless the carb is adjusted accordingly to account for the fuel/mix and air mixture from the carb.  Thats what many forget.
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Offline John Mc

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Re: AT fuel mix
« Reply #39 on: October 09, 2018, 09:40:36 PM »
The less is more thing goes like this .For reasons unknown some have suggested that heavier oil mixes lean out the fuel to air ratio causing a lean burn .The fuel to air mixture always had been controlled by the carb .
True however most have missed the part in the book that tells that a richer fuel/oil mix results in a leaner fuel/oil mix, thus reducing the available fuel/oil mix for cooling and performance...........unless the carb is adjusted accordingly to account for the fuel/mix and air mixture from the carb.  Thats what many forget.
Did you mean a richer fuel/oil mix results in a leaner fuel/air mix? I cold see that if it increased the viscosity of the fuel/oil mix - the carb would pull less of it through, if it were not adjusted to compensate. I'm curious how much of an effect that would actually have the difference between 32:1 and 50:1 mix amounts to an extra 1.4 oz of oil in a gallon of gas.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow


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