# Okay lets clear this up please

#### Tennessee Thumper

More oil is leaner.Example 32:1 is leaner than 40:1.:)

#### Jaybird

##### Apprentice Goon
More oil means that there is less gas in a given space. Also more oil increases the viscosity(or makes it thicker), which means the mixture flows through the jet orifice at a slower rate, leaning the condition.

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by Jaybird
Also more oil increases the viscosity(or makes it thicker), which means the mixture flows through the jet orifice at a slower rate, leaning the condition.

For the 500th time, it has nothing to do with viscosity. :(
Jets meter by volume, and for a given volume being passed there is less gas when more oil is present. The effects of viscosity in this case are too minor to be relevant.

#### trl junkie

Member
C'mon, Rich!

Man, when I saw the post before Rich's this morn, I was tempted to "correct"
the obvoius misinformation, but I figured Richs response would be worth a laugh on this one--Cmon, Rich, get a cup of coffee in ya, and try again!! :) I have for years cringed when I hear people talking about the "richer" or "leaner" fuel /oil mixture. I will attempt to explain it in the most non-confusing, basic of ways:The terms "rich" or "lean" are directly relevant to the FUEL to AIR ratio--oil (as in 2 stoke) is a 3rd factor in the equation!--For example: a 32 to 1 mix will be leaner than a 40 to 1 mix because there is less FUEL, because it has been displaced by the additional 2 stroke oil.

#### Rich Rohrich

##### Moderator / BioHazard
Re: This is not Advanced Tech. Rich

Originally posted by Yamamoto

Calm down a tad......I get a bit bored with the simple topics but thats why there is general topic and YOUR advanced topic.

I'm not bored with the topic(OK, maybe a little :) ) , but I do get annoyed with the fact that everytime the topic comes up this viscosity nonsense gets dragged in to muddy things up. When misinformation gets repeated enough times it turns into fact for some people. It's the hallmark of psuedo-tech advocates worldwide.

Jaybird summed it up perfectly with
More oil means that there is less gas in a given space.

He unfortunately got sucked into the undertow of viscosity , and veered into MXA territory:eek:

#### a454elk

##### Mexicutioner
Wow, all I know is that the higher the ratio for example, 50:1 gives you less oil and the lower gives you more oil. Less oil, chance of seizing due to non lubrication (don't try this at home). More oil, chance of fouling and spooging. I found that at a higher elevation, the more oil seems to casue fouling due to the combo of richer fuel and no air! Good luck. I run at 35:1, seems fine.
Elk

#### John.T

Member
Maybe when I ever get the chance to go to a dirtweek rich can explain this to me, but I still see it like this
for you out there who think less oil means richer, run your bike at 500:1 and tell me how rich it runs!:p
Ill stick to my 40:1 thanks!

OR run your bike at 5:1 and tell me how lean it runs!

#### MikeT

Originally posted by Rich Rohrich

For the 500th time, it has nothing to do with viscosity. :(
Jets meter by volume, and for a given volume being passed there is less gas when more oil is present. The effects of viscosity in this case are too minor to be relevant.

Too minor to be relevant.... Thats the answer I needed. I knew that the leaner fuel/air mix was because of a lower percentage of fuel, because of more oil, but I didn't know to what extent viscosity played. Rich I'll take it as fact that it doesn't have that much of an effect but I can't really agree with you when you say that jets meter by volume. Correct me if I'm wrong but since they (jets) are an orifice, they meter flow. "Q" or the quantity of fuel is a product of area x velocity. Q=av. One main jet is different from another because of its orifice diameter, right? If you have a smaller a (area) you will get a lower Q or quantity of fuel. This is all saying that the velocity remains the same (which you pointed out should stay the same).

Does this sound correct? If not just point out the right direction.

Mike

#### MikeT

Originally posted by John.T
Maybe when I ever get the chance to go to a dirtweek rich can explain this to me, but I still see it like this
for you out there who think less oil means richer, run your bike at 500:1 and tell me how rich it runs!:p
Ill stick to my 40:1 thanks!

OR run your bike at 5:1 and tell me how lean it runs!

You are dealing with extremes and you cant really do that. No bike will run at 5:1 and no 2 stroke will run for long at 500:1. We aren't talking about extremes like that, only small variations in mix ratios. Like 26:1 being a lean mix and 50:1 being a rich mix. A bike will run in both mixes, but will you get the results you want? I believe that my parts will last longer at 26:1 than at 50:1 with the way I ride. I also happen to get less if not any spooge running at 32:1 whereas I used to get a fair amout of spooge at 50:1.

That's all we are saying.

#### Wolf

##### doooode
Originally posted by MikeT

I also happen to get less if not any spooge running at 32:1 whereas I used to get a fair amout of spooge at 50:1.

All of it makes sense except for that. I speak of my experience and mine only, but I have played around with 32:1,40:1,50:1 and one thing is pretty clear to me: 32:1 produces a lot more spooge than 50:1.

#### Casper250

##### Motosapien
I think the confusion comes from the wording of how things are being described. Kind of like gear ratios,when you use a lower gear ratio, you re actually rasing the numerical ratio. ex.10 to 1 is a lower ratio then 5 to 1.

Picture a glass of water, wich will represent gas. If you fill it to the top and took a rock, which will represent the oil, and droped it into the cup, the rock will displace the water and make some overflow. the bigger the rock, the more water that it will displace.

A ratio of 32 to 1 is a ratio that has more oil in the mixture then a ratio of 50 to 1 so it will displace more of the gas.

Now a motor only needs air and fuel to run on, the oil just provides lubrication. Since the oil is taking up some of the volume that normally would be gas, there is less gas to mix with the air. This is the lean condition that people are refering to.

Now it might be a little confusion in that when you add more oil, THE FUEL is RICH in oil, but the mixture causes a lean condition in the burning of the fuel.

Hope i didn't confuse you more....

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by MikeT
Rich I'll take it as fact that it doesn't have that much of an effect but I can't really agree with you when you say that jets meter by volume.

I must be missing something. You described a change in volumetric flow based on a relative change in orifice size . Where exactly do you disagree ? :)

Jets meter by volume but air/fuel ratio is a function of fuel MASS relative to air MASS trapped in the combustion chamber. There isn't a 1 to 1 relationship.

With enough information about the variables and enough math it is possible to determine mass flow through a jet but most jetting charts and formulas are based on volume and total fuel mass is implied .

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by John.T
Maybe when I ever get the chance to go to a dirtweek rich can explain this to me

I try not to suffer fools out here but I make it a point not to do it in real life. You'll have to find someone else to wade out there and save you from drowning in your personal sea of ignorance.:silly:

#### motometal

454, did you read any part of this thread?

The velocity thru an orifice will be relative to mass AND viscosity of the fluid pulled thru it.

Maybe you are right, Rich on the viscosity thing...could you (or have you) set up a simple test? All you need is a source of vacuum, an orifice, and a way to measure volume passed thru the orifice.

#### *william*

Member
Why don't you stick THIS through your orifice! :eek:

Sorry couldn't resist. Rich is spot on as usual. Some of you might want to review your junior high physics and mathmatics.

:D

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by motometal
The velocity thru an orifice will be relative to mass AND viscosity of the fluid pulled thru it.

I take it you've dealt with molding operations in the "metal" industry :)

Originally posted by motometal

Maybe you are right, Rich on the viscosity thing...could you (or have you) set up a simple test?

I've seen some ASTM D 445 data in a couple of papers, I'll see if I can dig up the specific references. I've never bothered to test it myself because of the number of variables that need to be controlled to get accurate results at flow rates this low. Things like density/temp of the fuel, and dilutent content(and type) present in the oil is tough to control. There wasn't enough difference between ratios in the research papers I've seen to warrant further study for my purposes.

In the end it doesn't really need to be this complicated. While it may be amusing to discuss the relative effects of viscosity as it relates to fuel flow the simple fact is the cross sectional area of two jets marked with the same number will vary FAR MORE than the difference in flow due to density or viscosity changes between 32:1 and 50:1 ratios. Good jets vary as much as 5% cheap jets can be closer to 10% variance.

So kids in the end if you add more oil to your mixture it will take up space and the odds are good that less gasoline will flow through a jet, all else being equal. Whether or not it will cause a change in the final trapped air/fuel ratio will depend on a number of factors. Feel free to describe this phenomena anyway you like, but the basic facts remain the same.

#### mopowa

Member
"the cross sectional area of two jets marked with the same number will vary FAR MORE than the difference in flow due to density or viscosity changes between 32:1 and 50:1 ratios. Good jets vary as much as 5% cheap jets can be closer to 10%"

A little off topic but more usufull than the original topic. :)
Does this mean the generic mikuni jets I get from a bin are no good. I notice mikuni jets have a symbol on them while these "generic" ones have an rd stamped on them. Are these "RD" jets cheap jets?:eek:

#### motometal

Venturing further off the topic, an interesting one to consider is water vs. mercury.

Obviously, the mercury has a much greater mass, but has a low viscosity (I suspect near or lower than water).

Some people think of heavy (dense) fluids automatically being of a higher viscosity, and this is simply not the case.

I would also note that the difference in net fuel entering the engine, say 32:1 vs 50:1 is easilly calculated (and put in the form of a percent). 32:1 would be about 97% fuel, while 50:1 is about 98%. I would have to ask, is this 1% difference even relevant???

Also considering some of the oil burns...I would think with 32:1, a higher proportion of this oil would be burned, therefore actually should be considered part of the "fuel".

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#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by mopowa
"Does this mean the generic mikuni jets I get from a bin are no good. I notice mikuni jets have a symbol on them while these "generic" ones have an rd stamped on them. Are these "RD" jets cheap jets?:eek:

Chances are pretty good that the REAL Mikuni jets will prove to be more consistent across the board.

#### Jaybird

##### Apprentice Goon
HOLD ON just one damn minute! Rich threw the butt-hat at ME this time...y'all get to cry later. (John...please...chill the &%\$ out...sheesh)

Now, I agree that the viscosity change of your fuel mix from 50:1 to 32:1 is a only a slight variance, but a variance none the less. I have a good grasp of the fuel mix thing, and I add the viscosity thing as a helper. Although it may not be the most contributing factor, the change of viscosity is easy for a spode to comprehend. That being said, if one keeps in mind that more oil means thicker, and obviously slower traveling through a given orifice than a thinner fuel, it may help one to distinguish the difference, albeit not the most important thing to remember. Maybe not. (shrug)

I have to agree that many more things come into play when dealing with fuel mix. Air flow, for sure. Speaking of which....I'd bet my eye teeth that many folks here who are stumbling with their jetting have filters that could supply enough oil to heat New England in January. I may be vying for another batt-hat fitting, but I'd venture to say that an over abundance of filter oil will have more effect on the engines performance than any slight variance in jetting or fuel mix.

On the jet variance, no doubt about that. I have two different 190's and they perform ever-so-slightly different from one another. I've often wondered if it would be a good idea to have a reputable machinist bore a small jet to the size one wants. I'm sure off-the-shelf jets are machined in a CNC set-up that can obviously have variances from the control.

Again, John...I plan on bringing my youngest son to DW and sure hope he doesn't have to see anyone get their knot flogged....nobody needs that kind of stuff. I thought I left all that sort of threatening when I quit racing dirt track cars. Relax and have fun, pal.

#### MikeT

Originally posted by Wolf

All of it makes sense except for that. I speak of my experience and mine only, but I have played around with 32:1,40:1,50:1 and one thing is pretty clear to me: 32:1 produces a lot more spooge than 50:1.

I think I might get less spooge with 32:1 than 50:1 because maybe the piston ring seals better and inturn bumps up the compression so the fuel and oil burns more completely. Thats the only thing I can think of. Seriously, I used to have spooge out the pipe silencer junction, and it would get all over the fender. I was mixing at 50:1 and using 927 oil. I then switched to 32:1 and Super M oil.....no spooge. Maybe it was more the oil than the ratio. All I can tell you is that combination works for me. Maybe it was the oil change but I have run at 26:1 also getting no spooge so you might want to try it. I guess you have to find out what works best in your bike.

#### MikeT

Originally posted by MikeT

Does this sound correct? If not just point out the right direction.

Mike

Well, I didn't have the time to get out my hydraulics book yesterday but I got at it today.

Rich (how many times do people say this) you are right. Q does equal volume flow rate. For some reason I didn't remember the whole thing. Thanks for the correction. I should have cracked the book earlier. Duh! :confused:

#### MikeT

Did I say DUH! :confused: :confused:

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by MikeT
I was mixing at 50:1 and using 927 oil. I then switched to 32:1 and Super M oil.....no spooge. Maybe it was more the oil than the ratio

It takes a TON of heat to get 927 to burn completely, so switching to an oil like Super M that takes a lot less heat to run clean would certainly account for the improvement.

#### Rich Rohrich

##### Moderator / BioHazard
Originally posted by Jaybird
Although it may not be the most contributing factor, the change of viscosity is easy for a spode to comprehend.

I guess that's the point where we disagree. I think your original point was the easier to comprehend spode or not :)
I wish there was a spode handbook we could refer to, or maybe we should just ASK IVAN :eek:

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