Gas related 2 stroke failures?

[shooter]

Comments directed towards “bad gasoline” as a cause of seized engines, rather than oil issues, are becoming more frequent every month.

What do you think is the major issue with today’s gasoline?

•Is it the ethanol in the EPA mandated oxygenated gas absorbing moisture?
•Less detergent additives in the gas & more deposits in the engine?
•Does today’s gas degrade faster?
•Is the mix oil separating out?

 

[sedanman]

I'm convinced it's the oxygenates. NY is using methanol. My Dolmar owners manual says "Fuels containing alcohol should NOT be used" That's why I now run MX2T at 32:1.

 

[bwalker]

Ethanol is a huge problem because its been known to come out of suspension. Say your saw is tuned for 10% and it gets 50% fuel. You guessed it. Seizure. Methanol does the same thing and is corrosive to boot. Both alcohols also attract water because of there hyrdophillic nature. This aggrivates corrosion and storage issues. If you have to run oxy gas use one that is oxygenated with mtbe. I would use mtbe amoco premium over any other gas. The trick to though is finding a bp/amoco station that sells bp/amoco gasoline.

 

[sedanman]

MTBE is outlawed in NY. It is seeping ito the ground water.

 

[stihltech]

gas

the rule of thumb is back to use it up in 30 days. I don't care how or what you mix, because this is a gas problem, not oil.

 

[shooter]

Stihltech - In your training seminars,any indication of what was happening to the gasoline after 30 days that made it unsafe to use?

 

[bwalker]

the rule of thumb is back to use it up in 30 days.

During the summer I would not let it sit that long. in the winter gas will go several months no problem. USING metal or carb apporved plastic cans helps.

any indication of what was happening

Sludge, varnish, octane degradation, light end boil off causing hard starting corrosion, etc.

 

[shooter]

sedanman - MTBE was outlawed in WI during early 2001 for the same groundwater contamination issue.

As Ben indicated, the lighter weight hydrocarbon molecules may evaporate in stored gasoline, especially in temps above 70-80 deg F. This causes the gas to combust less efficiently & create more deposits.

 

[tony marks]

this area ,i would still attribut failures to be user lack of knowledge related..
if gas causes one of mine to go.. it really
tick me off. not that it would matter to anybody but me.. id just enjoy the daydream of caneing whoever i could blame..

 

[Fish]

I just love a man that uses the word "hydrophillic".

I love going to tech schools and updates, almost every
failure is attributed to "bad gas".

On any other forums, this thread would have degraded
into a Stabil infomercial.

 

[tony marks]

what do dat mean.. anything like rabys.
had to shoot a kids dog rite in front of him once.. he was gonna grab his dog an save him inspite everything his mamma could say.. anyway that the same

 

[igetbisy]

mix ratio

Originally posted by sedanman
" That's why I now run MX2T at 32:1.

You should be careful mixing your fuel richer than manufacturers recomendations. how do you then adjust your air fuel settings, because if you do follow common procedure while running a 32/1 where 50/1 is recommended, you end up having to lean out your high settings to achieve desired and expected performance, thus creating an equal, or possibly even worse situation than if you accidentally mixed your fuel a little on the lean side of 50/1. lots of pistons with holes in them cause of this.

 

[bwalker]

Igetbusy, Go re read you post and think about what you said. More oil in the gas would necessitate a richer slightly richer mixture. In most cases the saws are not tuned close any way so many can jump from 50 to 32:1 with out any issue.

 

[igetbisy]

fuel to oil ratio, and fuel/oil to air ratio are two completely different variables. they do however have very similar affects on the performance, one can compliment the other. they sort of work together, when you have to much air, you burn a hole in the piston, to little oil, bearings, rings, and cylinder take it.
when the manufacturer says use 50/1 and then tells you to adjust for highest rpm, they have designed that carb needle and seat for those recomendations, when you buy a new saw, you even get a little users manual that emphasizes not to mix your fuel rich, and this is the reason for that.
now go back and read your post, How well do you understand carburation, and combustion? you sure seem to assume that I am a fool. so I hope there was a slight misunderstanding, or you just needed to vent or something, because what I said makes perfect sense, and you acted like I was way out there. unless you know that what i say is wrong, take it easy there big fella.
when i am out of line, by all means, rip into me!

 

[bwalker]

If you change the oil ratio you should retune the saw. That what adjustment screws are for. Max no load will be the same either way.

 

[igetbisy]

lets suppose we've got our saw properly tuned running 50/1. we all know that the last thing we want to do is turn the high screw in any more, why? because we would be leaning out the fuel/air mixture (less fuel, more air) into the combustion chamber, which results in a hotter combustion, which will burn a hole in your piston, melt piston to cylinder, etc.
now, we take the same saw, and put a richer fuel/oil mix into it, (more oil) and fire it up. But now it is not revving like it was before, and we know that it runs just fine and safely at the higher rpm. so we take our little screwdriver, and turn that high screw in a little more until we get the saw running as fast as we expect it to.
what we've done, is lean out the air/fuel mixture to a level that is going to burn too hot for our little aluminum piston to withstand. It doesn't matter how much oil is lubricating the saw, the heat from too much air per unit of fuel is going to melt down the piston.
Of course that is for those of us who push the envelope when we tune, simply backing the screw out a little more than normal will put you back into a safe combustion temp, but it happens all the time, and you've really got to understand the differense between air/fuel, and fuel/oil, and what each does, because both use rich/lean to describe, leading us to associate the two too similarly.

 

[sedanman]

I tune by ear and by how much power I have in the cut, too lean = no power. I check to see that i am not running over max permissible rpm with my tach (Stihl EDT-5). Thanks for your concern but I think I have a handle on how to make my saws live long and happy lives.

 

[tree monkey]

igetbisy, if you think 50-1 is the right thing to do fine, it's your saw. i've used 32-1 for 20 years with no problems. burnt holes in pistons is from timing, or to hot of sparkplugs. not oil.


if you think less oil is better then the next time you change oil in your car only use one qt of oil. think about how mutch money you will save.

 

[igetbisy]

now look! I'm trying to tell you something here, and you're just not listening!








































Just kidding! sorry, not trying to insult anyone's intelligence, I've got to remember who i'm talking to here, I've seen a few guys say that they cant understand how they blew their saw up, because they had put extra oil in the mix, and that is why, because in order to get it to run good, with so much oil, they had leaned out their carb too much.

 

[sedanman]

What you are saying has some truth to it. You are talking about a saw that is tuned to the edge of detonation and the only change is the mix ratio. In that case MAYBE you'd toast the saw. When you added more oil you theoretically leaned the air fuel mix but some of that extra oil is displacing air too. I went to MX2T at 32:1 because I could not control the quality of fuel I was getting from the gas station, I CAN control the quality/quantity of oil I add to the mix.