Switch from 50:1 to 60:1?

liv2day

liv2day

Platinum Level Site Supporter
Hoping to get some input. I read through the sticky as well as several threads on premix ratios and the spooge issue some have experienced with the Q-Stealth pipe (which I am).

Let me preface this with being relatively new to the jetting stuff. It took me a while to get it sorted on my KTM 300 and I haven't started messing with it on the GG yet.

The reason I haven't messed with the jetting is the throttle response is spot on for me. However, it does have a lot of drool coming from the Q-Stealth. I read that many have had issues with the Q and blame the pipe, but I'm wondering if changing my ratio might alleviate this.

I'm running Amsoil Interceptor at 50:1; ran the same thing on my 300 and had some drool issues early on (also running the Q), but it stopped.

I know there are lots of opinions on premix ratios, but I'd like to know if there are any potential hazards from changing. The majority of my riding is tight and technical - not much high speed. I rev the engine out, but it also spends a fair amount of time lugging.

Thanks :cool:
 
I'll be watching the replies with interest.

My 250 runs faultlessly and strong at all RPM's, and ive always run it at 50:1 as per told to me by the previous owner and the original owner.
I also have a Q-stealth silencer and suffer with some spooge. Ive tried 2 different oils.....neither was really any different to the other regarding spooge.
My riding is alos mostly lugging - but with the occasional 'on-pipe' blast.

Instinct tells me going to 60:1 isnt the magic answer long-term..........
 
liv2day said:
Hoping to get some input. I read through the sticky as well as several threads on premix ratios and the spooge issue some have experienced with the Q-Stealth pipe (which I am).

Let me preface this with being relatively new to the jetting stuff. It took me a while to get it sorted on my KTM 300 and I haven't started messing with it on the GG yet.

The reason I haven't messed with the jetting is the throttle response is spot on for me. However, it does have a lot of drool coming from the Q-Stealth. I read that many have had issues with the Q and blame the pipe, but I'm wondering if changing my ratio might alleviate this.

I'm running Amsoil Interceptor at 50:1; ran the same thing on my 300 and had some drool issues early on (also running the Q), but it stopped.

I know there are lots of opinions on premix ratios, but I'd like to know if there are any potential hazards from changing. The majority of my riding is tight and technical - not much high speed. I rev the engine out, but it also spends a fair amount of time lugging.

Thanks :cool:
Click to expand...
The way I hear it, the Q-Stealth is a spooge makin' machine. If I haven't learned anything else...Don't base your jetting preference on tailpipe spooge. If your throttle response is spot on, and you've got a clean plug(tan, light brown...whatever). Leave well enough alone;)
 
bowhunter007 said:
The way I hear it, the Q-Stealth is a spooge makin' machine. If I haven't learned anything else...Don't base your jetting preference on tailpipe spooge. If your throttle response is spot on, and you've got a clean plug(tan, light brown...whatever). Leave well enough alone;)
Click to expand...

This is the money!

In saying that Nato has informed me he gets no spooge from his 2012 300, but he rides pretty hard too. I had a dribbe that ran from the end of the plug back maybe 10-15cms in a small line after 4 hours of single track work and not spending much time at all on the pipe.

I think when the jetting is just right the spooge will be minimal, however in saying that go with the above. Jet for response. Also remember, all it takes is to be rich in one particular throttle opening and then spending some time there to start it happening.
 
The last time I pulled my plug, I could tell it was running a little rich - black and not tan (but boy do I love a good black ' n tan...lol).

I have my reservations about the Q, but after having initial issues with it on my 300, the pipe was great.

I'm tempted to throw a leaner pilot jet in and see if that does anything; given my typical riding conditions and the condition of the plug when I pulled it - what do you think?
 
The oil you use makes a different, oils with high ash such as Motul 800R and others tend to spooge more than say oils with less ash.

I have used Motul 800 for many years, I firmly believe that it is a great product for it's intended purpose-RACING with high RPM, heavy loads and high heat, mixed at the motorcycles MFR's recommended ratio. I have always had spooge using this oil, either trail riding or racing, it dosn't matter, it spooges. I would also say that my jetting is a little on the "fat" side, but, that is the way I like it. I'd rather be rich, than lean and burn a piston and cylinder....fame away if you want too...will not hurt my feelings one bit. ;)

Now, I've used Motul 710 and it burns much,much cleaner with almost no spooge, same jetting, same ratio same everything. That being said, others on this board have also said the same thing between the 800 and 710. There is something different in the make up of the oil, if it is less ash, so be it, it will and does burn cleaner with less spooge.

The TCIIQ is a french fry oil trap, just like it's little sister TCII. I rebuild mine several times a year due to the "drip" It's a dirty job, no doudt. We just had this conversation this past Saturday about my buddies Berg TE250, it had a snail trail down the entire canister...he called his the french fry trap...

I would not change the ratio to try and make the spooge go away.

I'd keep the ratio at what ever the owners manual states.

If your really serious about making the "Q" drip go away, rejet, rejet and rejet again. Or, play with different oils and find one that works the best for YOU!

I am in the process of trying some of Rock Oil 2 stroke injector oil, which is much like the 710, but I was told, burns a little cleaner. I have a brand new TCII mounted up with fresh packing and we'll see.

That's my .02 for what it is worth...good, bad or ugly....
Good Luck and Happy Trails!
 
liv2day said:
The last time I pulled my plug, I could tell it was running a little rich - black and not tan (but boy do I love a good black ' n tan...lol).
Click to expand...

Remember going from 50:1 to 60:1 makes the jetting richer, not leaner.
 
noobi said:
Remember going from 50:1 to 60:1 makes the jetting richer, not leaner.
Click to expand...

Gah...and this is where I always get confused...lol.

Let me see if I understand your statement correctly; reducing the amount of oil in the fuel actually means there's more fuel going through the carb to combust; and that's what makes it richer...right?

It's a memory stretch, but I think what resolved the spooge issue from the Q on my 300 was using a richer pilot jet (went from 35 to 38) and a leaner needle (N3CH #3 - feedback from KTMTalk). That combination eliminated the spooge and kept the throttle response spot on.

Given my previous success using Amsoil, I'd prefer to keep that a constant.

So, how to go about reducing the spooge? I don't mind a little, but there's a significant drool stream down the bottom of the pipe after every ride. One other thought, I also have the a/s at 1.75 turns out.
 
liv2day said:
Gah...and this is where I always get confused...lol.

Let me see if I understand your statement correctly; reducing the amount of oil in the fuel actually means there's more fuel going through the carb to combust; and that's what makes it richer...right?
Click to expand...

Correct.

I know you said your jetting performs well, but I would recommend pulling the carb and checking whats there and comparing to what others have in the jetting thread. There is usually a mention of spooge or not in those posts.
Might be as simple as a smaller pilot, or a leaner needle or something. Costs nothing to check, and you have to pull the current jetting to change it anyway.
 
Calling all mathematicians!

I'll agree that the point is true in theory, but I challenge anyone (even Jake!) to be able to tell the difference at the throttle resulting from the ultra minute mixture change due to going from 50:1 oil ratio to 60:1 oil ratio.
Please read on before throwing all the anecdotes at me.

I'll leave the math to someone smarter than I. However, think about the fact that the ideal air/fuel mixture is 15:1 and were talking about a change from 1 part in 50 to 1 part in 60 in only one part of the original 16. I'm betting that is a change so minute that it couldn't even be accounted for with adjustments so course as jets, clips, and needle taper.

Again, I'll leave the math to the arithmeticians. Perhaps, after lots of mathematics (please show your work!), someone can equate the actual mixture change by changing oil ratios to a common change in jetting. I.e, "going from 50:1 to 60:1 oil ratio is like changing your needle clip 1/20th of a step down on an N3CH taper needle, or going from a 168 main to a 168.28 main at the average fuel volumes burned by a 250cc two stroke in the middle of the RPM range at standard atmosphere."
Until someone does the volumetric comparisons I simply will not be convinced.
The answer to the question as to why one may notice a reduction in spooge when they go down to 60:1 is obvious: were talking about only the percentage of oil and not the ratio of oil to fuel in an overall ratio with air.
A change of 50:1 to 60:1 is a change from approx. 2% to 1.66% oil. Enough to notice a less messy tailpipe.

I intend no disrespect nor am I trolling for a heated debate. I'm truly curious. My Forrest Gump mind tells me the math, if I could do it accurately, wouldn't validate the accepted postulate that a change from 50:1 to 60:1 oil ratio is a significant enough change in mixture to re-jet.
 
I used to run my 09 300XC at 50:1. I only used Motul 800 and or Klotz Technoplate. They have a higher flash point but I never had serious spooge issues. I also had the FMF on it. I firmly believe that jetting is the biggest issue when it comes to the mess coming out the tail pipe. The only time that it was an issue, was when the bike was started cold. But that goes for every other 2T I have been around.
 
Math based answer - The difference between 50:1 and 60:1 is less than 1 tablespoon oil difference per gallon of gas.

Gut based answer supported by experience making more severe changes in gas:oil ratios without perceivable effect on jetting - Seasonal changes in air temperature and humidity will affect your jetting more than this minor change in oil between these two ratios.
 
When I clean the bike I wipe the spooge off with a dab of solvent and forget about it. So long as the bike runs well, it's not a big deal. (50:1 fully synthetic)
 
andoman said:
Calling all mathematicians!
Click to expand...

I can math.

So lets take a 250cc 2 stroke, running at 5000rpm.

That's cycling 0.25L x 5000/min of air/fuel mix. 1250L/min, or 20.83L/sec.
At 20.83L/sec flowing through a carb of, say, 38mm diameter. Thats 18.37m/s air velocity though the carb. Which comes from 20.83L/s / ((pi*(0.038m/2)^2) /1000L/m^3)

If we assume the engine operates at the 'ideal' 15:1 air/fuel ratio.
Then its 19.52L/s of air and 1.301L/s of fuel. Of which, at 50:1, 98% is gasoline.
So its actually 1.301L of gasoline and 0.025L of oil
Now lets assume that all the fuel is vapourised completely and it all came through the main jet only. This just simplifies my lunchtime calculations.
The vapour density of gasoline is around 3-4 times that of air, which is 1.2kg/m^3, so 3.6-4.8kg/m^3. Lets assume it 0.004kg/L just because.
The liquid density of gasoline is between 0.71-0.77kg/L, lets say 0.75kg/L.

So if we flow 1.325L/s of vapour fuel mix, that is 1.325x0.004 = 0.0053kg/s
Which must of come from 0.053/0.75 = 0.00707L/s of liquid fuel mix.

Now, iv'e assumed that the vapour and liquid densities of the fuel mix are approximately that of pure gasoline, because the density of oil is not hugely different to that of pure gasoline, its around 0.75kg/L for gasoline, and around 0.8-0.9kg/L for oils, and seeing as the're mixed at around 2%, the effect on density is small. 0.98x0.75 + 0.02x0.9 = 0.753 which is ~ 0.75.

So lets consider a main of 160, which is 1.6mm diameter, so the velocity through is must be (0.00707/(0.0008^2*pi))/1000 = 3.516m/s.

Now, lets assume that this engine is in its 'sweet' spot, and the ideal fuel delivery is based on engine dynamics and the flow through the main jet is defined by pressure differences across it, this is actually how it works too by the way.

So lets change the mixture ratio, but the engine dynamics stay the same, so the engine mass flow is the same, and the flow through the 160 main jet is the same. So 0.00707L/s of liquid fuel mixture. Which as before, is 0.0053kg/s fuel mix, thus 1.325L/s fuel vapour
But now lets make is 60:1 instead of 50:1, so its 1.66% oil and 98.33% fuel
So we have 1.303L/s of pure gasoline instead of 1.301L/s. I'm assuming that all the oil falls out of suspension and is not burnt with gasoline.
We're still flowing the same total volume of 20.83L/s, but theres more fuel in it, less oil, the same amount is air. So 19.52L/s air and 1.303L/s fuel vapour, which gives an air/ fuel ratio of 14.98 instead of 15.0038. Based on the rounded numbers I used to start with.
Pretty much no difference.

Now we could have gone straight to that derivation from the 50:1 v 60:1, but you asked about changes in the carb.
So, if we wanted to go back to the 15:1 ratio with the 60:1 fuel / oil mix.
As before, flowing 20.83L/s of fluid, 15:1 ratio air/fuel.
So 19.52L/s of air and 1.301L/s of fuel, 1.301L/s fuel is actually 1.301L/s of gasoline, so it must actually be 1.323L/s gas/oil vapour mix through the carb.
Which is 0.007056L/s gas/oil mix liquid.
However, I set the velocity across the main jet before at 3.516m/s.
So recalculating the main jet size based on flow rate and velocity, 0.007056/3.516/1000 = 0.0000020m^2. Solve for main jet size, 0.0000020 = r^2*pi, r = 0.000799, which gives a mainjet diameter of


1.598mm, equivalent to a 159.8 size mainjet.

So, your gut feeling of a change of 50:1 to 60:1 making sfa difference is correct.

A change to 40:1 gives a mainjet of 160.5
You would have to go to 20:1 before a change in mainjet was needed to accommodate the change is fuel, and even then, its only to a 162 main.



Now take all of this with a pinch of salt, or whatever the stupid expression is, it is very off the cuff as I could think of relating one thing to another. It also assumes steady state in the engine and carb, which is ridiculous of itself, but I didn't want to get involved with differentials.
 
Last edited:
noobi said:
I can math.

So lets take a 250cc 2 stroke, running at 5000rpm.

That's cycling 0.25L x 5000/min of air/fuel mix. 1250L/min, or 20.83L/sec.
At 20.83L/sec flowing through a carb of, say, 38mm diameter. Thats 18.37m/s air velocity though the carb. Which comes from 20.83L/s / ((pi*(0.038m/2)^2) /1000L/m^3)

If we assume the engine operates at the 'ideal' 15:1 air/fuel ratio.
Then its 19.52L/s of air and 1.301L/s of fuel. Of which, at 50:1, 98% is gasoline.
So its actually 1.301L of gasoline and 0.025L of oil
Now lets assume that all the fuel is vapourised completely and it all came through the main jet only. This just simplifies my lunchtime calculations.
The vapour density of gasoline is around 3-4 times that of air, which is 1.2kg/m^3, so 3.6-4.8kg/m^3. Lets assume it 0.04kg/L just because.
The liquid density of gasoline is between 0.71-0.77kg/L, lets say 0.75kg/L.

So if we flow 1.325L/s of vapour fuel mix, that is 1.325x0.04 = 0.053kg/s
Which must of come from 0.053/0.75 = 0.0707L/s of liquid fuel mix.

Now, iv'e assumed that the vapour and liquid densities of the fuel mix are approximately that of pure gasoline, because the density of oil is not hugely different to that of pure gasoline, its around 0.75kg/L for gasoline, and around 0.8-0.9kg/L for oils, and seeing as the're mixed at around 2%, the effect on density is small. 0.98x0.75 + 0.02x0.9 = 0.753 which is ~ 0.75.

So lets consider a main of 160, which is 1.6mm diameter, so the velocity through is must be (0.0707/(0.0008^2*pi))/1000 = 35.16m/s.

Now, lets assume that this engine is in its 'sweet' spot, and the ideal fuel delivery is based on engine dynamics and the flow through the main jet is defined by pressure differences across it, this is actually how it works too by the way.

So lets change the mixture ratio, but the engine dynamics stay the same, so the engine mass flow is the same, and the flow through the 160 main jet is the same. So 0.0707L/s of liquid fuel mixture. Which as before, is 0.053kg/s fuel mix, thus 1.325L/s fuel vapour
But now lets make is 60:1 instead of 50:1, so its 1.66% oil and 98.33% fuel
So we have 1.303L/s of pure gasoline instead of 1.301L/s. I'm assuming that all the oil falls out of suspension and is not burnt with gasoline.
We're still flowing the same total volume of 20.83L/s, but theres more fuel in it, less oil, the same amount is air. So 19.52L/s air and 1.303L/s fuel vapour, which gives an air/ fuel ratio of 14.98 instead of 15.0038. Based on the rounded numbers I used to start with.
Pretty much no difference.

Now we could have gone straight to that derivation from the 50:1 v 60:1, but you asked about changes in the carb.
So, if we wanted to go back to the 15:1 ratio with the 60:1 fuel / oil mix.
As before, flowing 20.83L/s of fluid, 15:1 ratio air/fuel.
So 19.52L/s of air and 1.301L/s of fuel, 1.301L/s fuel is actually 1.301L/s of gasoline, so it must actually be 13.23L/s gas/oil vapour mix through the carb.
Which is 0.07056L/s gas/oil mix liquid.
However, I set the velocity across the main jet before at 35.16m/s.
So recalculating the main jet size based on flow rate and velocity, 0.07056/35.16/1000 = 0.0000020m^2. Solve for main jet size, 0.0000020 = r^2*pi, r = 0.000799, which gives a mainjet diameter of


1.598mm, equivalent to a 159.8 size mainjet.

So, your gut feeling of a change of 50:1 to 60:1 making sfa difference is correct.

A change to 40:1 gives a mainjet of 160.5
You would have to go to 20:1 before a change in mainjet was needed to accommodate the change is fuel, and even then, its only to a 162 main.



Now take all of this with a pinch of salt, or whatever the stupid expression is, it is very off the cuff as I could think of relating one thing to another. It also assumes steady state in the engine and carb, which is ridiculous of itself, but I didn't want to get involved with differentials.
Click to expand...

WOW! That hurt my head and made my eyes bleed :p
 
Very Well Done! What are your thoughts on the difference in viscosity?
 
Noobi, that was awesome! Thanks!

Looking at a density altitude chart, we see that just the change in temperature from the chill in the morning as we unload the bikes to the heat of the afternoon has a much greater effect on jetting needs than changing pre-mix ratios.
 

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