2 stroke oil to fuel ratio

[Aussie treesmith]

I can't turn my ported 660 over when cold and the decomp valve closed without seriously worrying about breaking something

Edited November 16, 2013 by Aussie treesmith
grammer

[openspaceman]

The smoke is blue because it is an aerosol (colloidal suspension of solids in a gas), Particles of Incomplete Combustion finely dispersed in the exhaust such that they interfere with the light and appear blue in reflection. They are normally black soot based particles. This is similar to why a a similar suspension of oils in a liquid (i.e. milk an emulsion) is white.

 

In order for the two stroke oil to not ignite at all, the chamber temperatures and pressures would have to be so low as to not completely burn the petrol as well. The pressure alone from the petrol igniting would ignite most oils, let alone the fact there is fire and spark and heat in there beforehand. The amount of unburnt fuel and oil pouring out of the exhaust at that point would simply be ridiculous.

 

That's a non sequitur, nowhere in my post did I say that oil did not burn. What I said is that the blue colouration in the smoke is a phenomenon of a sol. In this case the particles are hydrocarbon that has not burned completely. Often it is lubrication oil but that is not because it will not burn, rather that the conditions in which it is exposed to combustion do not enable it to burn completely.

 

In the good old days before engines were as well made, oils less well formulated and carburettors a bit hit or miss it wasn't unusual to see a newish car sat idling with a wisp of blue coming from the exhaust. Often from oil dribbling down a valve guide and we've all seen it in wood smoke from a chimney.

 

Yes the flame temperature in a petrol engine (about 2000C) is high enough to burn oil and much will be burned well but think about what that oil is there for. It enters the engine as a solution in petrol, the petrol evaporates and the oil condenses as a mist on the cooler engine parts. Eventually it does burn but not completely, essentially oxygen molecules from the air preferentially strip hydrogen from the hydrocarbon and then the remaining carbon rich molecules start to burn, if they don't complete this burning before the temperature falls during the power stroke (less than 2.5 milliseconds at 11krpm) then they leave as PICs.

 

Even when finely divided in a diesel engine more time and more air is needed to burn the droplets which is one reason diesels are inherently slower revving than petrol engines.

[Gerbutt]

Been using my hedge trimmer/strimmer combo on 50:1 instead of 25:1 for the last two days and it's been sound. It's stopped smoking like Dot Cotton and it seems to be running cooler too, it used to get ever so hot after an hour!

[GardenKit]

Been using my hedge trimmer/strimmer combo on 50:1 instead of 25:1 for the last two days and it's been sound. It's stopped smoking like Dot Cotton and it seems to be running cooler too, it used to get ever so hot after an hour!

Result!

 

Next step, Aspen.

[wyk]

This is a quote from Randy, AKA Mastermind from AS. He has ported hundreds of saws and repaired hundreds more.

 

"32:1 just makes me feel all warm and fuzzy.

 

I don't believe I'd see any failures at 40:1 either.......but

 

The 390XP has been known to lose the crank and/or PTO bearings. That same saw on 32:1 will last and last. The 372XP has a crank that can be a little intolerant of static compression pressures of 200 psi and more.....unless they are run @32:1.

 

I torture test a few saws of my own......trying to kill em with compression. I have to know what they will or will not be able to handle. Since I started using H1R @ 32:1, I've not lost a crank...... "

 

He also has said that 50:1 is EPA nonsense, to paraphrase. And has recently shown what Amsoil Saber at 80:1 can do to a MS660 Crank(the bearings seized and grenaded much of the motor).

Edited December 7, 2013 by wyk

[GardenKit]

But to all the users of standard saws and other hand held two strokes, do not be afraid of 50:1 with quality oils.

 

It is the correct ratio and will not do any harm at all.

 

I have not ported any saws but have sold and repaired not hundreds, but thousands, of two stroke machines, all of which have bee run at 50:1 with no problems. As long as it is reputable oil.

 

As I have said before though, use cheap oils at your peril, and if you do then its best to mix a bit stronger.

[Eddy_t]

This is a quote from Randy, AKA Mastermind from AS. He has ported hundreds of saws and repaired hundreds more.

 

"32:1 just makes me feel all warm and fuzzy.

 

I don't believe I'd see any failures at 40:1 either.......but

 

The 390XP has been known to lose the crank and/or PTO bearings. That same saw on 32:1 will last and last. The 372XP has a crank that can be a little intolerant of static compression pressures of 200 psi and more.....unless they are run @32:1.

 

I torture test a few saws of my own......trying to kill em with compression. I have to know what they will or will not be able to handle. Since I started using H1R @ 32:1, I've not lost a crank...... "

 

He also has said that 50:1 is EPA nonsense, to paraphrase. And has recently shown what Amsoil Saber at 80:1 can do to a MS660 Crank(the bearings seized and grenaded much of the motor).

 

Mastermind also extracts much more power from the saws and ups the compression considerably, which causes the saws to run a hell of a lot hotter and straining the moving parts, meaning the lubrication needs to be higher. He also tunes the saw for the mix, most of the UK arbs do not tune the saws, and are ill equipped to do so, as 95% do not own a tach, and as a few have said on AS, whilst you can tune by ear, the tach is vital for intrinsic things, such as clutches on the large old saws.

 

 

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[wyk]

Mastermind also extracts much more power from the saws and ups the compression considerably, which causes the saws to run a hell of a lot hotter and straining the moving parts, meaning the lubrication needs to be higher. He also tunes the saw for the mix, most of the UK arbs do not tune the saws, and are ill equipped to do so, as 95% do not own a tach, and as a few have said on AS, whilst you can tune by ear, the tach is vital for intrinsic things, such as clutches on the large old saws.

 

 

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I'm with ya there. I use 40:1 myself on all my saws. Most Arbs and foresters I know run their saws on the rich side. Sometimes ridiculously so. So 32:1 would cake them up prolly inside a few months.

 

But bear in mind, that Mastermind also sees a lot of non-ported saws. Hundreds is a tad conservative. He ports hundreds a year, so prolly has seen thousands of standard saws. He also advises running 32:1 in them as well. I was raised in the 40:1 era. Perhaps he was raised in the 32:1 era. Shrug. Use good oil is all I gotta say, I guess.

[wrsni]

But to all the users of standard saws and other hand held two strokes, do not be afraid of 50:1 with quality oils.

 

It is the correct ratio and will not do any harm at all.

 

That is the definitive statement of the entire thread.

[wrsni]

I was raised in the 40:1 era. Perhaps he was raised in the 32:1 era. Shrug. Use good oil is all I gotta say, I guess.

 

I was raised in the 25:1 era but I've altered my view as the oil companies have improved their products.

 

Also bear in mind that a chainsaw engine is a pretty tame two stroke engine by overall standards, they're not going to be that difficult to lubricate properly really.