066 Just stops. What gives???

[Lakeside53]

Stihl saws over here require a minimum of 89 (USA)... We just try to get everyone to run "premium" at 92. The regular and premium vary by state and area though. In Montana (western), the pump regular is 85 or so, and in Washington it's 87.

Running regular (low octane) is bad... the saws run much hotter. I see it in the plugs, cyinders, pistons and mufflers. Easy to spot... Stihl "says" they won't warranty saws burnt out by use of regular gas but it's hard to prove.

From 1995 - point 3.. Does not only refer to oxygenated fuels. Also in all the user manuals now.

 

[GPH85]

Lakeside is absolutely right about the synthetic oil vs. the dino oils. With todays cross hatching capabilities you are actually better off to use a syn over a dino. In order to understand this I will try to explain what happens on a microscopic level when an engine breaks in with the different oils...

Engine broke in with dino type oil - on a microscopic level, metal pieces or the rough edges that must seal or mate to one another, break or chip off = longer break in time and more wear, it breaks off because the oil can't provide the shear or friction protection capabilities to keep the metal edges from hanging and chipping. The metal edges chip and wear down until they have a good smooth sealing surface.

Engine broke in with syn oil - on a microscopic level, the metal pieces or surfaces are rounded and smoothen down instead of broken off = almost no wear and quicker seating or sealing.

These two different break-in methods or rather oils used for breaking in an engine have been proven on larger engines on engine dyno's. The dyno's, when synthetic oil was used as a break-in oil would show the engines to be pretty much seated up and broke in after 3 - 5 pulls, where as a normal dino oil would take nearly all day to get the same "nice patterned or charted" dyno readings.

However I have heard, from some of the older engine builders, that the longer an engine takes to break in, the longer it would last. This really makes no sense to me, since it would appear that you would have more wearable material if the engine broke in quicker. I know people who have broke in engines with syn haven't had many to if any problems doing it as long as the machining is good and consistant... (if the cylinder has "all around" type cross hatching and machining, it has shown that you are better off to use a dino oil and let it break off the edges since the cylinder has to be reshaped anyway / good machining = no problem)

 

[Ekka]

I'm gonna step up to our 95 octane rating now after reading that.

wahoooo, more grunt!

So, just go synthetic off the bat hey.

But if it looks like a car engine bore after a hone you go dino right?

 

[Canyon Angler]

Thanks for the info Lakeside. I, too, was under the impression that a mineral-based oil was better for break-in but I guess maybe not. Are you sure the Stihl guys weren't just playing "CYA" with their own products (the Stihl syn oil)?

 

[timberwolf]

Was the muffler of this fallen 066 opened up?

That pea sized hole they have for a muffler outlet holds a lot of heat in.

 

[Southern Boy]

Factory muffler without any mods. I think I'm going to gut it and expand the existing hole 2x. I have a small cheap HF wire welder that would be good for fixing it right up.

The more I think about it, the more I feel that the piston was scored when I got it. It has NEVER run full throttle for move then a couple of minutes. I have run 93 octane gas through it and only a small amount. My mix may have been a little light for hard work, but not too light. While topping the tree with it, it was getting extremly hot then, but never died. I, also, noticed that it just didn't seem to have the power that I would have expected from a saw this size. Oh well. No since crying over spilled milk. Fix it and go have fun.

The only thing that I really am not sure of, how do I check to make sure my gas tank is getting good air flow?

 

[GPH85]

Yes, you are better off to use a regular "dino" type oil after doing any type of "touch-up" type cross hatching or hand made cross hatching.

(Guess I should have stated that)

Sorry,
Greg

 

[manual]

Hey Southern Boy,
I'm willing to bet that your saw had problems when you bought it.
you sound to conscientious to burn your saw up. By the look at the saw dust build up and air filter usage this saw has had a hard life.
Now before you spend 300.00 dollars plus to the "Sthil foundation for the rich".
Try using muriatic Acid, Q tips and schotch brite pads to clean up the cylinder.
If all is well all you have to do is get a piston and ring set.
Good luck and nice pics.

 

[timberwolf]

May want to make sure there are no splits or leaks in the carb boot, the the crank seals are ok, and the carb is cleaned out, these things could all contribute to a lean sieze.

 

[Lakeside53]

The only thing that I really am not sure of, how do I check to make sure my gas tank is getting good air flow?

You put a vacuum pump on the fuel line and make sure the tank vent lets air in... A mighty-vac or similar from the auto parts store will work fine. Empty the tank first...

You may as well invest in a vac and bulb pump - you do need to pressure test the entire saw to make sure the problem won't repeat. It is possible the last owner simply ran it on straight gas, messed it up, and then disposed of it on ebay.. Sorry for your bad luck..

 

[Canyon Angler]

you are better off to use a regular "dino" type oil after doing any type of "touch-up" type cross hatching

Greg - Are you saying that we should use dino oil to break in a saw (since it'll have "fresh" cross-hatching), rather than the Stihl syn oil for example?

Lakeside - Are you saying we should use Stihl syn oil for break-in?

You guys seem to disagree on this if I'm reading you right.

 

[Lakeside53]

No disagreement. For a factory cylinder, synthetic is fine. After a "hone" - depends on the hone... but I'd be generally happy with Syn.

 

[GPH85]

I'm agreeing with Lakeside on this one... Depends on the hone

Usually as stated, a hone won't do too much to the Nikilsil, so as far as being out of round is concerned in saw cylinders you shouldn't have anything to worry about as far as the honing oblonging the cylinder in any shape or form. You can break out the bore gauges or T gauges to measure several places down through the cylinder to check for any out of round areas. NOW if we're talking about bigger engines that your "touching up", absolutely measure and more than likely never use a syn as a break in oil. A new car or vehicle or something like this - no problem, but not for "touch ups" on bigger engines (more stress on walls and not as good of cylinders = will more than likely be oblonged or out of round) Saws and small cylinders like these where there isn't that much stress on the cylinders - shouldn't be a problem...

Syn should be fine for "redone" saw cylinders unless boring or anything else of this nature is being involved.

New saws - there is no problem at all with using syn as a break in oil (you can read my first post on the subject to see that it is actually better to use the syn on a new saw)

Hope this doesn't further confuse anyone and will help to clarify some things...
Greg

 

[Canyon Angler]

OK, I gotcha. Guess I was reading you all wrong. Thanks.

 

[josgmctk]

I had a new piston that looked like yours after doing some milling.
about half way thru the 2nd tank of gas the pulse line failed
and the saw ran out of gas in the cut 30 inch cherry. cleaned
the cyl and put in another new piston and rings. replaced the
pulse line, now I will try this again.