Constant revving and reluctance to turn off

[Al_Smith]

Even more .The 038 and it's kinsmen have a tough cylinder .I had one that literally grenaded a piston and it didn't even leave a scratch on the cylinder .You can probabley save the cylinder .A Metior piston is pretty good if you go that route.I'd change the seals while you're at it . Sicker cats than that thing have lived ,good luck .

[Coreytroy]

Throw away that danged Amsoil too while your at it .

What is the 'Amsoil' ?

[bandmiller2]

Corey, Al is referring to the synthetic 2 cyc. oil that recommends 100/1 mix. Most of the old timers here use a thicker mixture than 50/1. If you got the time go back and read the oil war posts. Frank C.

[Al_Smith]

Amsoil is something that would probabley work great at at least 40 to one ratio .--the oil wars gotta luv it . :D

Now that said why in the world would you run anything Amsoil or no at what 90 to 1?  What is the bassis for that ? Royal plum purple maybe .Snake oil ? Gettin wound up now better stop .

[Coreytroy]

Ok, I see said the blind man to his deaf mate !

I use Valvoline 2 Stroke Oil. Normally 42:1.

But am not 100% that I used the correct mix last outing, as I rushed my gear to get out and cut while I had the time, and feel I may have grabbed and unmixed fuel from a container that had 50:1 on it, but in hind-sight, it may have been straight fuel, that I added a tad of oil to in stead to increase it from 50 to 42:1.

Maybe I should be running it at more like 40 or 35:1 in the future. What do you guys recommend as a ratio?

[Ianab]

I use Valvoline 2 Stroke Oil. Normally 42:1.

That should be OK. Folks will debate oil mixes all day (The legendary Oil Wars), but that mix is in the "sensible" range.

But the revving with no power would suggest overheating from a lean mix, not a lack of oil. Not enough oil tends to kill saws too, but they just quietly seize up and wont go any more....

Ian

[Coreytroy]

That is my assumption Ian of what occurred.

I may just buy the cylinder/piston package, and replace them. Will try to clean up the original cylinder first though.

I will post some pics when I do this.

All the advice here is much appreciated, as mechanically I am a novice.

[thecfarm]

Good luck with your fix. I use a magic marker on my gas cans. And to tell you the truth I don't know why. I only have one mix,40:1. I'm the only one that deals with the cans and mixing. I only have one can that I mix in. I use my chainsaw quite a bit,so that is a five gallon can. No gas EVER goes into the 5 gallon can without the oil going in FIRST. I also buy the highest grade of gas that I can find at my local gas station,for all my small motors. Another debate.  :D I also shake the cans before I put into smaller one gallon cans and those small ones gets the shake treatment before I fill the saw. I only have certain gallon containers that my mix gas goes into. Than a diffeant type that I use for the lawnmower and wood splitter. Yes,the extra cans cost a little,but they last for years.
And when I pour the gas into the saw,I'm still a looking for that blue color of the gas. Keep things the same,no getting confused and trying to remember what is what from a week or two ago.

[Hilltop366]

Not mentioned yet, plugged or restricted fuel tank vent will cause lean air fuel mix.

[DDDfarmer]

The final nail in the coffin for my SOLO 656 saw was when the carb boot came loose.  I have never heard a small motor run that fast before.  I first played with the throttle then the kill switch which I was turning off/on/off.  the only way I was able to shut that motor down was to bury it in the wood to stall.  I was able to pull over after it cooled down but sounded like it was full of gravel, it would sputter but not run.  they took it back on warranty but gave me a worse lemon. 

[ehp]

yes most likely air leak BUT if the saw will not shut off with kill switch then look at how much ethanol is in your gas , if to much ethanol in the gas it will burn down a motor real fast and the saw will not shut off either , Just because the gas pump says no ethanol or up to 10% that does not mean your gas is 10% , we did a test on high test pump gas around here and found as high as 28% ethanol in the fuel , not good for 2 stroke motors as most normal 2 stroke oils will not mix with that much ethanol

[Andyshine77]

I've done some fuel testing around town. The levels of ethanol varied from almost none to around 15%, you never know what you're going to get. The pumps here are also unmarked, most people around here have no idea are fuel even has ethanol in it.   

[Al_Smith]

Sounds good maybe but to get either diesel combustion or like a glow engine you'd have to have a huge amount of heat and the right fuel .

With a glow engine for example you have the catalitic effect of a platnum wire in the glow plug in conjuction with mentanonal mixed with nitromethane for glow engine plus compression ratios approaching diesel ratios .You have none of that in a stock chainsaw .

If it were by some slight chance a glowing ember of carbon the timing would be off so much it would hardly run and certainly not accelerate .

I just don't buy that theory .

[JohnG28]

I get the alcohol being bad for the engine and potentially making for a meltdown when run. But like Al, I just can't see how one of these engines would run let alone accelerate if the kill switch was working correctly.  ???

[ehp]

ethanol is worse than methanol for glow plug in the motor and the glow plug is the end of the spark plug and that is why we modded the end of the spark plug to run these types of fuel,  believe me I have built lots of motors to run on both fuels and if your motor is set to run on mixed gas and you get a heavy mixture of ethanol it will take off on you just like methanol and if you donot know how to get the motor to quit it will not until its melted which you would be surprised that it does not take very long plus most normal 2 stroke oils will not mix with any gas that is 15% or more ethanol .

[joe_indi]

I recall that in 1999-2000, when I met a German Stihl engineer for the first time and we were discussing seizures in the 046 in those days, he had suggested that it was due to poor quality of fuel and had asked me to use the saws like they do in Brazil, since there was a fuel issue there too, because of blended fuels (Gasahol)
Instead of the regular .3mm cylinder gasket #1128 029 2304
He advised me to try the .8mm low compression gasket #1128 029 2306.
And it help save quite a lot of pistons, and cylinders

So, I was looking up  the 038 in Stihl's extinct Electronic catalogue.
There is a regular cylinder gasket #1119 029 2302
And a low compression gasket #1119 029 2303. Probably for lower quality fuels since the MS380s and present MS381 come from Brazil.
The lower compression would also prevent what mechanics call 'dieseling', the after run of a gasoline engine even with ignition switched off. Which is caused by hot cylinder deposits that act as a glow plug to ignite the compressed fuel.
If its too much of a problem getting the low comp gasket, the simple fix is to use two regular gaskets.This will bring down the compression slightly and reduce heat.

[Coreytroy]

This is what the cylinder looks like.
Just a clean up required? What do you think?
If so rather than buying some cleaning acid and/or honing tool that i would never use again, was going to take it in to my local Stihl service centre for them to clean for me.



But then found this:

My question is how to you remove the manifold rubber from the carbi ?
From the cylinder side or do i need to disassemble the saw more to do this?
I am assuming there another clamp behind the carbi, but not sure how to access it ?

[JohnG28]

Looks like you found the reason for your problems with that torn boot. The cylinder doesn't look bad, but hard to tell in the picture how much transfer there is. Under the exhaust port looks a little rough. Not sure if a dealer will do that or not for you. I'd imagine they will say you need a new one.

[Andyshine77]

You have to remove the carb. When you do that you can pull the boot out from the cylinder side. When you reinstall the cylinder, put the boot on the cylinder than mount everything as you pull the boot through the carb box opening.

Really can't tell much from the pics, but it looks like some of the plating under the exhaust port may be gone. Could just be the bad pic.

[Coreytroy]

You have to remove the carb. When you do that you can pull the boot out from the cylinder side. When you reinstall the cylinder, put the boot on the cylinder than mount everything as you pull the boot through the carb box opening.

Really can't tell much from the pics, but it looks like some of the plating under the exhaust port may be gone. Could just be the bad pic.

How do I remove the carb is it screwed on somewhere ?
Hard to see how it is fitted on.
Also, if I run my finger across the section under the exhaust port, it feels like a deposit not a dip.
I might try buying some Bondall hydrochloric acid and using a cotton bud to try to remove any aluminium from inside, then use a scotch rite cloth to shine it up what I can.

[Andyshine77]

You have to remove the carb. When you do that you can pull the boot out from the cylinder side. When you reinstall the cylinder, put the boot on the cylinder than mount everything as you pull the boot through the carb box opening.

Really can't tell much from the pics, but it looks like some of the plating under the exhaust port may be gone. Could just be the bad pic.

How do I remove the carb is it screwed on somewhere ?
Hard to see how it is fitted on.
Also, if I run my finger across the section under the exhaust port, it feels like a deposit not a dip.
I might try buying some Bondall hydrochloric acid and using a cotton bud to try to remove any aluminium from inside, then use a scotch rite cloth to shine it up what I can.

Yes hydrochloric/Muriatic acid will do the job, make sure it doesn't get on any other bare aluminum like in the ports.

Take the air filter off and you'll see two M5 nuts, remove them, disconnect the hoses and linkage. This is simple nuts and bolts type stuff, If you can't see something, remove something so you can.

[Coreytroy]

Thanks, I will have a better look at the air filter side for the M5 nuts.

[Coreytroy]

If the kill switch isn't getting it something is wobbling plus it has a loose grounding bond .

Sounds to be if possibley the shock mounts went bad causing the engine to rock out stressing the intake boot .If you haven't seen it before you cannot believe how fast a saw will run with an air leak ahead of the carb on just idle .I'll bet an easy 7-8000 rpm .I have seen it,twice as matter of fact on the same saw .Both times torn shock mount  and torn boot .

Your assumption may yet be 100% spot on.
I am going to check the annular buffers, to see if they have caused the manifold split.

[celliott]

I just went through the same thing on a Stihl 028 I repaired. Yes, you have to take the carb off, then kind of squeeze the boot to get it through the plastic piece. Make sure you don't lose the metal ring on the carb side of the boot, and don't forget to put it back when you reinstall!
On the 028, there was two nuts, then the linkage and the fuel\impulse line holding the carb on.
Also on the 028, that top rubber AV mount was a bit loose/sloppy. Combined with someone probably yanking on a stuck saw is what most likely tore the boot.

If you don't want to buy muriatic acid, do you have any toilet bowl cleaner? Alot of cleaners have some hydrochloric acid in them. While not quite as strong, they do dissolve some of the aluminum. Then it's a matter of elbow grease to get the rest of it.

[Andyshine77]

Pulling on the saw will rip the intake boot for sure. But remember fuel will deteriorate the rubber boot just like the fuel lines over time.