066 stalls when hot

[Adkpk]

The final diagnose on the scored piston was water in the gas.

 

[THALL10326]

The final diagnose on the scored piston was water in the gas.

Hmmmmmmmm thats a odd one must say. Most saws don't run well enough with water in the gas to turn enough RPM's to score a piston. May well have been the cause though, I'm just saying I've never ran across that.

Yank that muffler and have a look. Your gonna have to do it out of curiosty so do it and let us know what you find..

 

[Justsaws]

The final diagnose on the scored piston was water in the gas.

I have been hearing people say that they were told water in the fuel ruined there piston a lot lately. I do not know how much I believe that. In my experience even a little tiny bit of water and the saw will not run. I will qualify that statement with telling you that I do not own a saw as new as yours nor am I a saw mechanic.

If I was you I would find a different shop and give them a try. It sounds as though they might be able to do better or at least no worse. Water in the gas and old fuel can be questionable causes that need better proof when it comes to a piston and cylinder replacement. Almost always the scoring that I am dealing with is caused by air filter, carb., bearing, or air leak problems.

Do what Thall10326 and Lakeside suggest as they are full to the top with knowledge about Stihls. Pull your muffler and look for piston scoring.

I hope it is and easy fix. Good luck.

 

[Adkpk]

It was a old can of gas that was the culprit. After we used up the gas I brought with my brother turned to his gas that sat under the for like EVER.
Anyway, ya to Thall and Lakeside they spend so much time answering peoples questions on this site I wonder how they make a living.
I don't have a problem with my saw shop, they are pretty cool. I told him about the Arborist site he laughed, lol, and said he didn't have time to use the internet. (made me think of Lakeside, ha, ha) I wish I didn't have to travel 30 minutes to his shop or I wouldn't be asking you guys. I will take off the muf and have a look. I do what to look for. I have the old piston and jug. I'll post a pic of someday if I remember to. I will also check the gas tank vent. But not going till Monday.

 

[Lakeside53]

I assume you've already done this but clean out your tank, then put some Isopropal acholol in it and swish it around. That will remove any traces of water. Throw your fuel filter away... and fit a new one.

 

[Four Paws]

As for water in the gas, I feel the same way as Justsaws - In my experience even a little tiny bit of water and the saw will not run. Water will actually plug the tiny passages and membranes in the carburetor, and the engine will die from fuel starvation.

 

[rmihalek]

Maybe the "new" gasolines with 10% ethanol as well as an ethanol co-solvent are more prone to having water dissolve in them. After all, I don't think ethanol is soluble in gasoline, which is why the co-solvent has to be added. And, I think we all know that ethanol and water mix freely! Water in the fuel would certainly lean the fuel:air ratio since there will be less gasoline burned per unit volume of fuel due to the presence of water.

 

[Sprig]

The final diagnose on the scored piston was water in the gas.

Yep, was just going to post a filter solution and ya beat me too it, glad its simple. Don't chuck the filter, dry it out, water I have found will 'plug' a good filter, turns the fuel into a mushy goop, soak and clean with gas or acetone (no sparks or smoking eh!), let it dry thoroughly, keep as a spare.
Just my 0.02$ fer the stinkin' hot day (100 or near in the shade right now).
Btw, we never use regular gas here in our saws or small machines as it seems to have much more of a water problem, premium or nothing imho.

COLD

Serge

 

[Adkpk]

update

Read it and weep, I am. Looks like I scored my second piston. The pic isn't real good but I think you can see the scored area. Damn, why? I was using 38-1 premium grade gas. I don't get it, my other saws are running well. I'm disgusted, please help me think this saw is worth the money it's costing me.

 

[THALL10326]

Read it and weep, I am. Looks like I scored my second piston. The pic isn't real good but I think you can see the scored area. Damn, why? I was using 38-1 premium grade gas. I don't get it, my other saws are running well. I'm disgusted, please help me think this saw is worth the money it's costing me.

As suspected. Now something is causing those pistons to fry like that. Not saying anything was done wrong by whoever replaced it the last time but it do appear they didn't find out what caused the first piston to go. They said water in the gas the first time, seems they were mistaken. The same issue has killed your second piston. Always have to find the source of the problem before the problem can be solved. Changing pistons/jugs will not solve whatever is killing them...

 

[Adkpk]

As suspected. Now something is causing those pistons to fry like that. Not saying anything was done wrong by whoever replaced it the last time but it do appear they didn't find out what caused the first piston to go. They said water in the gas the first time, seems they were mistaken. The same issue has killed your second piston. Always have to find the source of the problem before the problem can be solved. Changing pistons/jugs will not solve whatever is killing them...

Thanks Thall, I am bummed.

 

[BlueRidgeMark]

As suspected. Now something is causing those pistons to fry like that. Not saying anything was done wrong by whoever replaced it the last time but it do appear they didn't find out what caused the first piston to go. They said water in the gas the first time, seems they were mistaken. The same issue has killed your second piston. Always have to find the source of the problem before the problem can be solved. Changing pistons/jugs will not solve whatever is killing them...

Most guys who wear the name of "mechanic" (or technician or engineer or doctor!) are nothing more than parts swappers. They have no clue how to troubleshoot. They have learned a few fixes that go with a certain bucket of problems, and when they see one of those problems, they throw one of their fixes at it. Spray and pray.


Then there are real mechanics who get to the root of the problem. Understanding how things work, they can work backwards from the problem to probable causes, and know how to narrow things down to THE cause, and then fix it.


Sounds like Tom is in the second category.

 

[stihlatit]

Read it and weep, I am. Looks like I scored my second piston. The pic isn't real good but I think you can see the scored area. Damn, why? I was using 38-1 premium grade gas. I don't get it, my other saws are running well. I'm disgusted, please help me think this saw is worth the money it's costing me.

Hey Adrpk lets have a beer and a tear togother here is what I found when I tore down my 066 Magnum today. I popped the piston last week. I will try to clean my jug and maybe get away with just a piston and rings. Otherwise change the jug as well. Then get it pressure tested to make sure seals are ok. Then fire it up and do acarb re-adjust. Pictures are below.

 

[THALL10326]

Thanks Thall, I am bummed.

Well fine sir let me say, that saw has a bottom end built like a tank. Its well worth fixing but its got to be fixed correctly this time so it doesn't keep frying those pistons. The problem with it has yet to be corrected causing the samething to happen over and over. On my table it would be checked over every which way possible after the reapir to insure it doesn't happen again. I'm guessing that saw is running too lean for some reason. Needs to be corrected, thats all it needs to stop frying those pistons....

 

[stihlatit]

 

[stihlatit]

 

[stihlatit]

 

[THALL10326]

Hey Adrpk lets have a beer and a tear togother here is what I found when I tore down my 066 Magnum today. I popped the piston last week. I will try to clean my jug and maybe get away with just a piston and rings. Otherwise change the jug as well. Then get it pressure tested to make sure seals are ok. Then fire it up and do acarb re-adjust. Pictures are below.

Yikessssssssssssss anutter hot one there. Arnie what Rpm was that saw running. I'm guessing above 14 grand from the looks of that psiton, thats a hot one for sure..........

 

[stihlatit]

 

[stihlatit]