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for the masters...2T running rich vs lean regarding mixing gas

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Please read my comment entirely before answering.

It is my opinion that when discussing whether a bike is either running rich or running lean, the discussion is based primarilty on the mixture between air and fuel.  Too much fuel for conditions, and the bike is said to be too rich.  Too little fuel for conditions, and the bike is said to be too lean.  The jetting/carburation is then adjusted for proper running.

An alternate, but separate  discussion on whether a bike is running too rich or too lean is often regarding the mixture of gas and oil.  For example, a 2 stroke that is smoking is regarded by some as running too rich. If a lot of spooge is on the tail pipe, it is also regarded as running to rich.  If its fouling plugs , its regarded as too rich. There is too much oil in the gas:oil mixture.

However, and here is the subtlety of my question.  If you are comparing a 20:1 with a 60:1 gas:oil mixture, the nomenclature of a rich vs a lean mixture is inconsistant amongst riders.  Some say that a 60:1 mixture is more lean than a 32:1 mixture, while others state the opposite.  

Historically, I always referred to a 20:1 mixture as more rich than a 60:1, because there is more oil in the mixture with more smoke,  more tail pipe spooge, and more likely of fouling a plug. But that was challenged by an old fellow who races vintage 2 strokes on asphalt tracks.  His argument was that there is less gasoilne to burn in a 20:1 mixture vs a 60:1 mixture and that in fact creates a lean condition and in addition more likely for the engine to run too hot and seize.  Wow!   Completely different perpsective. More smoke, more spooge, more oil on the plug, but too lean!!!  This blew my mind.

 

So, do you consider a  20:1 mixture more rich, or more lean than a 60:1.  Or should I not even describe a gas mixture as rich or lean and only reserve the words rich and lean with regards to jetting/carburation only. 

What do you think?  

 

 

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I have heard that before. More oil to gas can create a lean condition. I've also talked to guys I respect who say its bogus. 

My opinion is that if there is more oil to gas and the same volume being pulled through. There logically will be less gas to burn. Which equals a leaner running bike. 

Have no evidence to prove this though.

Also I wonder if the percentages of oil to gas we are talking about will make it a moot point. 

Edited by Bobatsea
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This has been beaten to death.

Lean/rich refers to air to fuel ratio and nothing else, period. Oil mix is oil mix and has nothing to with lean/rich. Remember that and you won't have any problems. You can run 20:1, and if jetted correctly, won't smoke at all. However, you could be running 60:1 oil mix and smoke like crazy if the jetting is too rich.

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10 minutes ago, SS109 said:

This has been beaten to death.

Lean/rich refers to air to fuel ratio and nothing else, period. 

This is what I suspected.  Its the only point that makes sense in all circumstances.

 

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Please read my comment entirely before answering.
It is my opinion that when discussing whether a bike is either running rich or running lean, the discussion is based primarilty on the mixture between air and fuel.  Too much fuel for conditions, and the bike is said to be too rich.  Too little fuel for conditions, and the bike is said to be too lean.  The jetting/carburation is then adjusted for proper running.
An alternate, but separate  discussion on whether a bike is running too rich or too lean is often regarding the mixture of gas and oil.  For example, a 2 stroke that is smoking is regarded by some as running too rich. If a lot of spooge is on the tail pipe, it is also regarded as running to rich.  If its fouling plugs , its regarded as too rich. There is too much oil in the gas:oil mixture.
However, and here is the subtlety of my question.  If you are comparing a 20:1 with a 60:1 gas:oil mixture, the nomenclature of a rich vs a lean mixture is inconsistant amongst riders.  Some say that a 60:1 mixture is more lean than a 32:1 mixture, while others state the opposite.  
Historically, I always referred to a 20:1 mixture as more rich than a 60:1, because there is more oil in the mixture with more smoke,  more tail pipe spooge, and more likely of fouling a plug. But that was challenged by an old fellow who races vintage 2 strokes on asphalt tracks.  His argument was that there is less gasoilne to burn in a 20:1 mixture vs a 60:1 mixture and that in fact creates a lean condition and in addition more likely for the engine to run too hot and seize.  Wow!   Completely different perpsective. More smoke, more spooge, more oil on the plug, but too lean!!!  This blew my mind.
 
So, do you consider a  20:1 mixture more rich, or more lean than a 60:1.  Or should I not even describe a gas mixture as rich or lean and only reserve the words rich and lean with regards to jetting/carburation only. 
What do you think?  
 
 
You are wrong, do not use the words rich or lean in relation to oil ratio at all. Rich or lean are only in relation to the bike getting more or less fuel than it can efficiently burn through your chosen metering device.
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8 minutes ago, HevyRotashunz said:
1 hour ago, G-Berm said:
Please read my comment entirely before answering.
It is my opinion that when discussing whether a bike is either running rich or running lean, the discussion is based primarilty on the mixture between air and fuel.  Too much fuel for conditions, and the bike is said to be too rich.  Too little fuel for conditions, and the bike is said to be too lean.  The jetting/carburation is then adjusted for proper running.
An alternate, but separate  discussion on whether a bike is running too rich or too lean is often regarding the mixture of gas and oil.  For example, a 2 stroke that is smoking is regarded by some as running too rich. If a lot of spooge is on the tail pipe, it is also regarded as running to rich.  If its fouling plugs , its regarded as too rich. There is too much oil in the gas:oil mixture.
However, and here is the subtlety of my question.  If you are comparing a 20:1 with a 60:1 gas:oil mixture, the nomenclature of a rich vs a lean mixture is inconsistant amongst riders.  Some say that a 60:1 mixture is more lean than a 32:1 mixture, while others state the opposite.  
Historically, I always referred to a 20:1 mixture as more rich than a 60:1, because there is more oil in the mixture with more smoke,  more tail pipe spooge, and more likely of fouling a plug. But that was challenged by an old fellow who races vintage 2 strokes on asphalt tracks.  His argument was that there is less gasoilne to burn in a 20:1 mixture vs a 60:1 mixture and that in fact creates a lean condition and in addition more likely for the engine to run too hot and seize.  Wow!   Completely different perpsective. More smoke, more spooge, more oil on the plug, but too lean!!!  This blew my mind.
 
So, do you consider a  20:1 mixture more rich, or more lean than a 60:1.  Or should I not even describe a gas mixture as rich or lean and only reserve the words rich and lean with regards to jetting/carburation only. 
What do you think?  
 
 

Read more  

You are wrong, do not use the words rich or lean in relation to oil ratio at all. Rich or lean are only in relation to the bike getting more or less fuel than it can efficiently burn through your chosen metering device.

Thank you

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Premix ratio should not be considered a variable.  Generally speaking the correct ratio is 32:1.  Some bikes and some riders that run lower RPM and less throttle can run less oil but you don't save much money doing so.  You could also call this a 3% premix ratio.  97% gasoline and 3% fuel.

40:1 would be 2.5%.  60:1, which I would consider irresponsible for most applications and likely to cause premature wear or engine failure, is about 1.6%.  The difference between 32:1 and 40:1 as far as jetting is concerned is extremely small.  Not enough to worry about.

Pipe spooge and smoke are always jetting with the exception of a crank seal failure which is possible but not common.

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Some learning going on.  Can you hear it?

 

If I've got this right and the logic is consistent: 

A 20:1 fuel mixture in a bike that is jetted to run 32:1 will be running lean because there is less gasoline available to detonate in each drop and will have the potential to run too hot and seize. In addition, at the same time being at risk to fouling a plug due to too much oil.  So, running lean and fouling plugs.  

I got it?

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Lean enough to make a difference?  Not unless it was jetted marginally to begin with.

20:1 will not foul a plug.  Bad jetting fouls plugs. 

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To all, the actual numbers are less critical than the actual concepts.  And all your input is greatly appreciated.

Edited by G-Berm
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Back in the good old days, fouled plugs were caused by marginal ignition systems. These days, jetting...

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The amount of oil can change the viscosity of the fuel as well. More oil, more viscous, potentially leaner. I have never done any testing to see if it’s substantial.

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It makes a difference, even if you don't easily notice it. Even different oil's at the same ratio can run different, it can more, or less contribute to the combustion.  Why they say , pick an oil, pick a ratio, jet, and stay with it. 

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using these viscosities at 15.6C (60F)- 15.5 for gasoline, 792 for Castor 927, 477 for Motul 800 Off Road (using oil data plugged in to this site I was able to find their viscosities at 15.6 Celsius: https://wiki.anton-paar.com/en/astm-d341-viscosity-temperature-extrapolation/?tx_apcalculators_calculator[action]=calculate&tx_apcalculators_calculator[controller]=Calculator

for a fuel/oil ratio of 30:1 Castor 927 gave a mixed viscosity of 41.5 and Motul 800 gave 31.1

for a fuel/oil ratio of 50:1 Castor 927 gave a mixed viscosity of 31.1 and Motul 800 gave 24.8

(by "mixed viscosity" I mean the oil and gas are mixed together)

so from one oil to the next the viscosity of gas mixed with oil can greatly vary and from one mixture ratio to another they can greatly vary.

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Less gas is leaner. Doesn't matter if it's lean jetting or excessive mix oil, the results are the same.

You can litterally lean out a bike that is running rich, by adding more oil in the fuel.....but it's going to cause other issues like spooge.......but it does work. 

Ideally, the mixture should be based on what the bike brand and oil brand recommend......and it should never change, or you will just get confused.

 

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Less gas is leaner. Doesn't matter if it's lean jetting or excessive mix oil, the results are the same.
You can litterally lean out a bike that is running rich, by adding more oil in the fuel.....but it's going to cause other issues like spooge.......but it does work. 
Ideally, the mixture should be based on what the bike brand and oil brand recommend......and it should never change, or you will just get confused.
 
Add low flashpoint oil and you wont have spooge.

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More oil=less gas, lean. Yet spooge? Conundrum eh? All 2 strokes can become slobbering engines, a few things to consider....
1) this is the day of synthetics for a reason, castor oil is the best lube for a 2 stroke no doubt, but it has a high flashpoint so even if jetted properly there is a good chance that if you go from say a moto track into a single track then back to the moto track there will be spooge because some of the oil didnt burn while idling in woods so it blew out. Synthetics have a low flashpoint and so it burns cleaner with very good lubrication. Spooge shouldnt be on the muffler of a well jetted 2 stroke using synthetic.....ever, as far as im concerned. Slower riders or more technical terrain riders should use synthetics. Main jet sand tracks are best served with castor.

2) air screw..... if you dont adjust your air screw for the day you may end up blubbering on the pilot jet a bit because its running a bit rich at the air screw, chokey has a good solid technique ive used for years now, operating temps, turn idle up a tad, turn air screw in. If it tries to die good! Turn it slowly out until rpm is highest, ride around a bit and adjust an 1/8th turn this way or that to maximize response. So, you could be off on the air screw, loading with fuel at idle, but lean everywhere else and have spooge....

3) adjust jetting for YOU! I ride softer then my brother, but im faster. I prefer a leaner more responsive needle that reacts quickly with little movement, he needs richer jetting because he screams the bike on that main jet and uses a clutch versus roll on type riding.... so adjust and tailor for you. Lean makes it rev fast but not pull long, rich will pull longer but not be clean getting there.

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On 1/19/2019 at 12:06 AM, G-Berm said:

If I've got this right and the logic is consistent: 

A 20:1 fuel mixture in a bike that is jetted to run 32:1 will be running lean because there is less gasoline available to detonate in each drop and will have the potential to run too hot and seize. In addition, at the same time being at risk to fouling a plug due to too much oil.  So, running lean and fouling plugs.  

I got it?

Almost. Of course if you add more oil your bike will run leaner. But, and that is really overlooked, have you ever tried to imagine how minimal the change is? I dont know anyone who could feel the difference between 50:1 and 60:1 or 40:1. Your engine will not run hot and it will not seize it may be more prone to eventually foul a plug...

If your bike is jetted right and you use the oil the manufacturer specified, not the brand just the tech requirements and it still spooges, then the reason(s) could be:

  • the oil has a high or very high flash point. Best example Motul 800, which has an extremely high flash point of 252°C (486°F)
  • you ride on the pilot circuit. Meaning you do a lot of slow stuff, never rev high
  • your bike has technical characteristics which encourage spooge

An oil with low flash point, like Putoline MX9 or Castrol Power 1 (both at approx. 167°F) will be fine as long as its within the specs the engine manufacturer requires. So what you check is, specs, flash point and -most forgotten- what is the highest mixture the oil manufacturer allows. While Amsoil Saber, Fuchs Titan S100 will work up to 100:1 other oils don't but most will work with 60:1 except Castrol Power 1 where the oil manufacturer limits the mix to 50:1. Would you use it in a KTM requiring 60:1? No. Your engine would survive even if you mix it 70:1 but its better to listen to the manufacturers they have a reason why the say use it up to....

Edited by Doc Brown

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