Pre-mix oil talk

[BriarcliffMx]

hmm, never though of it that way. Kinda the opposite of the humidity deal in the summer, less oxygen, blah blah blah.

 

[flyin polack]

Back in the day...'80-'86 we ran Amsoil lat 100:1 with no issues at all. When they came out with the Dominator at 50:1 we switched to that and still run it. Amsoil used to have a policy that if your motor had an oil related failure they would pay for it. I blew up my dad's chain saw one time and they actually picked the saw up at the dealer and tore it apart to find dirt inside. The tear down was no charge...

I remember reading an article in MXA (in the 80's) on 2-stroke lube that Ron Lechein did. They tested all ratios and 40:1 actually was the highest they would recommend going. They sighted ring seal and the 40:1 had measurable HP gains on the dyno compared to 50:1.

One thing to remember is that synthetic oils will not always allow accurate ring seating due to the superior lubricating qualities. I always run a tank of CCI, which is petroleum at 32:1 so that the rings seat better. It's a bit of a pain...but quality maintenance is well worth it for me...

 

[GeorgiePorgie]

Because adding oil to gas creates more total volume of fuel but less of it is gas depending on the mixture ratio.

Most of the time you fill a 5 gallon can, so would 2.56 oz in a 5 gallon can make that much difference for total volume after being mixed and dumped in the gas tank of the 1.5-2.0 gallon tank??

Even if you're mixing exactly the right amount the volume of fuel isn't going to be that much different?


Or I guess it would still be the same if you mixed exactly enough or in a 5 gallon can. 32:1 is 32:1. I don't know.

 

[PitRacer]

It's pretty simple math. If you put 2.56 oz of oil into 5 gallons of gas, the total volume of liquid fuel is now 5 gallons + 2.56 oz.

You are taking a certain measured quantity of liquid and adding to it another measured quantity of liquid. This in turn adds up to a new, greater total quantity of liquid.

Or you can look at it this way. If you are running 40:1 ratio that means there is a total of 41 parts gas/oil combined.

 

[MarctheSharc]

Think about it this way:</O
<O</O
Every time the piston comes around the volume in the combustion chamber is fixed. …..Think about it.
Ok, got that concept…
Now remember that only the gas burns, not the oil (it sticks around and lubricates)…. Ok, that makes sense.
So, since the volume is fixed and the oil don’t burn. The more oil in the mixture means less gas in the mixture.
Add in the amount of air (fixed by the carb dia) and you’ll see that the more oil in the mixture the “leaner” the mixture actually is.
It’s a fine balance…..
The oil mixing ratios has nothing to do with “leaning out or richening up” for power on a two-stroke.
It's for lubrication .....not performance...

 

[TwentyThreeMX]

Think about it this way:</O
<O</O
Every time the piston comes around the volume in the combustion chamber is fixed. …..Think about it.
Ok, got that concept…
Now remember that only the gas burns, not the oil (it sticks around and lubricates)…. Ok, that makes sense.
So, since the volume is fixed and the oil don’t burn. The more oil in the mixture means less gas in the mixture.
Add in the amount of air (fixed by the carb dia) and you’ll see that the more oil in the mixture the “leaner” the mixture actually is.
It’s a fine balance…..
The oil mixing ratios has nothing to do with “leaning out or richening up” for power on a two-stroke.
It's for lubrication .....not performance...

ahh perfectly put.

 

[BigYac]

all the discussion on premix ratios has got me wondering, if one had major engine failure and it was traced back to a problem with the premix, would the oil manufacturer cover the repairs assuming you were running the recommended ratio according to your bike size?