Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: bigbore on December 10, 2009, 06:40:58 AM
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I am a big believer of heavy oil usage.I run 32:1 in the 1980 YZ465.It's only on the 2 OS piston and it's no garage queen.Even with my 1984 RZ 350 (oil injected) I run the pump on the heavy side.The photo is the head from the RZ after 13000 miles.Notice the lack of carbon.Also after 13K the pitsons were worn out.However the bore is striaght and true to the tune of 2 ten thousandths.Just like it was new.Rings were also worn out.The cylinder in my avatar is the one I'm talking about.This is no stock RZ,ported,head welded and remachined for the set-up,carbs.pipes,ect.Oh and the RZ has 40,000 miles (all but 1601 mine) on it and is 1st over.Been through a bunch of pistons and rings.Crank #3 is going in.Enough with the specs.
I am an advocate of synthetics or the bean if you've the time to take care of it.I've spent a bit of time studying rheology,tribology and CFD so I can get a little deep about this.Synthetics simply work better .Better lubrication,little to no smoke even at high loads.I do not understand the current practice of thin oil ratios.I'll provide empirical evidence that more oil=more power.Click here (http://www.bridgestonemotorcycle.com/documents.htm) and scroll down to the Cycle magazine article and download it.It's a photocopy of a 1978 article.Please read it.There's some other stuff worth checking out there too.
Here's the head.See the lack of carbon?The goo is oil pushed to the exhaust port by transfer wash.Wiped it off with a rag.
(http://img.photobucket.com/albums/v606/TRexRacing/RZhead.jpg)
EDIT:The oil used in the RZ is Amsoil Interceptor.
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I can assure you that the oils from 1978 are not the same as today. That being said, premix ratios affect jetting. And from experience, most carbs are jetted from the factory for ratios closer to 20:1 than 40 or 50:1. So there is more to the "more oil is better" thinking than just the ratio.
So....................if you have spent some time with a certified tribologist you will know that for a commercially produced premix, they fret over viscosity. Not of the oil in the bottle, but how the oil, mixed with fuel changes the viscosity of the fuel. Oil is so complicated that to the casual observer it's simply ignored what technology there is in oil (of all types).
I never EVER go by what the owners manual says about premix ratio. I go by what the guy who blended the oil in the bottle say. So yes, I mix by the label. If it says 20:1 than that is what I do. If it says 80:1, I'll do that and jet accordingly. And there are problems with this. Most guys aren't tuners, don't understand all these things, and the comic book media won't teach it because I don't think THEY know it. Just look at Motocross Action mag. Guys actually write in and get TUNE UP tips from them. Even though they don't ride at the same level, premix at the same ratio, ride at the same elevation and other factors. I think it's outrageous that MXA even attempts this jive. It's stupid, and does a disservice to 2 stroke riders by keeping them ignorant of their machines. I have no doubt that you can get an oil that will lubricate efficiently at ratios above 100:1. 99% of the market could not afford them. That same percentage of riders would have trouble with their tune up.
I don't want to come off as arrogant, because I am not. I am concerned with 2 stokes and how they are perceived in the world of motorcycles.
I spent more than 2 hours (that's a lot if you think about it) with a tribologist who works for a niche market oil manufacturer. That was some of the most educational time I spent on the phone ever. We covered additives that produce power, how THEY develop an oil, what they use for base stocks and friction modifiers (we talked about 4 stoke oils as well) and why, if properly lubricated, and engine will make the same power at any premix ratio, providing the tune up is corrected for the change of oil.
Man, I gotta write that book................. ;)
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I've spent a lot of time with a flowbench screamin' in my ears,dyno tuning (2 and 4) and riding.Regardless of the oil's configuration more is better.Longer life,more power how could these be drawbacks?Empirical evidence is what matters.Everything works in theory but no one lives there.You basically have one problem.At,say 100:1 there physically is not enough oil to cover the territory.I don't care how good it is if it can't cover the parts it cannot lubricate.I have not yet met anyone,either rider or tuner who considered that.Combined with the horrible swill called fuel (loads of solvents) that we see now the lack of lubrication is critical.Care to discuss that aspect?
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As I have stated before...I don't try to out think the tribologist. I don't need to. As for needing enough oil to cover all regions: think of the volume of fuel that moves through the engine. Now consider that most guys have oil DRIPPING out the of the pipe (the dreaded spooge).
That is excess oil not used for lubrication. And it costs HP to run the crank in excess oil. Dyno experience should show that. That is why Pro Stock pans are huge, the oil pumps pull 15-20 inches of vacuum and they run low tension oil rings and back cut compression rings (among other things).
It's all academic. I'm not saying that at 100:1 you would not encounter problems in certain situations. Lets say a long high gear pull, followed by a low RPM, high load hill climb. At low throttle openings, the available oil is just not there.
I know there are oils that will work at super high dilution rates. I don't argue with the guys who design the oil.
There are also environmental concerns. Greater dilution rates use LESS oil overall. Synthetics also don't produce smoke when correctly tuned.
So everyone can bark about low dilution rates and lubrication, but until I see the spooge and smoke stop, it's all irrelevant. That's a waste of oil and HP.
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I didn't address your position about the "swill" called fuel (gasoline) we are stuck with today. I do not advocate race gas in a 2 stroke unless you have altered port timing, compression ratio and the pipe. You just don't need it. But you can't run "regular" either. The difference between the two is significant. I don't feel like typing it all out, but there are many reasons not to run race fuel in your bike. From timing and jetting issues to cost and power output.
However, I do use an additive that is not available anymore. There are good reasons to run pump premium for fuel in your dirt bike, especially if you ride year round. And these were expressed by a fuel manufacturer.
I also want to point out that 2 strokes require significantly LESS lubrication than do plain bearing applications. This is due to roller bearings on the crank and wrist pin.
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I'm just not seeing the spooge.Jetting is spot on and that makes a huge difference.And at 32:1 it smokes a bit cold,little to none warm.Again 2nd over at 29 years old.Seems like we'll just have to agree we disagree.And I won't even start about the benefits of heavily leaded oxygenated wonder juice and the power it produces. :P
(http://img.photobucket.com/albums/v606/TRexRacing/YZpipe1.jpg)
(http://img.photobucket.com/albums/v606/TRexRacing/YZ4.jpg)
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I've said it before, but my '67 bike is still running the original piston. Not sure what our ratio is, but it does smoke a bit and isn't a garage queen. This thing has been ridden half-way to the moon and back and continues to run well. Again, I don't know what our ratio is, but we use Castrol and I can say it's a damn sight more than 40:1.
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I'm just not seeing the spooge.Jetting is spot on and that makes a huge difference.And at 32:1 it smokes a bit cold,little to none warm.Again 2nd over at 29 years old.Seems like we'll just have to agree we disagree.And I won't even start about the benefits of heavily leaded oxygenated wonder juice and the power it produces. :P
(http://img.photobucket.com/albums/v606/TRexRacing/YZpipe1.jpg)
(http://img.photobucket.com/albums/v606/TRexRacing/YZ4.jpg)
I don't consider 32:1 to be outrageous. I am premixing at 40:1, as per the manufacturers recommendation. Any non-synthetic oil is just not woth it, including bean oil, at any ratio, regardless of results. Jetting is the cause of 99% of spooge and smoke.
I said I use a fuel additive (not an additive but a conditioner), never commented on lead and oxygenation.
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Madscientist I have to agree with you on some points, and disagree on others. I believe using the manufactorers ratio's are the best way to go in most situations. There is one however that I found I had much better results using extremely high ratios(60-80:1). This was with Trials bikes( low compression, mostly low revs), and these ratios worked well. I did however have my bikes jetted correctly. No bean oil? I have had very good luck with it. I just don't use it when it is below 40 degrees(seperation can occur at temps below 40). Below 40 I use a blend (Super M). On the fuel issue, I have always used race fuels (C-12 predominately, we are in VP's home town) based on the consistancy! I jet all my dirtbikes using the same fuel and oil,type,and ratio. I do not want my fuel, or oil to be a variables that change. The pump gas here is attrocious regardless of octane rating. My lawnmower doesn't even like it!
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Smoke and spooge are indeed primarily a product of poor jetting, not "too much" oil. You can indeed use all that oil if the bike is jetting correctly for the mix being run. Assuming proper jetting for the mix used, I am with the "more oil is better" crowd. However I'm quite comfortable running at 40:1, especially for trail riding. I will NOT run 50/60/80/100:1 regardless of what the oil manufacturer claims.
Madscientist,
I'm interested to read the info coming from your source in the oil industry. Should be interesting!
J.
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:P Politics-Religion-Oilmix,.....we will never come to a common agreement
Its just not possible.
We have discussed it for many years,probably since engines are in the world.
It will never change.
But here a nice story out of my expirience.
ISDT Germany 1962.I am a team member for Germany.
My bike DKW 175 cc.Gas from ,oil from Castrol.Mix 20-1.(that was a common mix in this days).
Optimol Oil Werke,from Munich(just around the corner from Garmisch Partenkirchen),comes (for the very first time in Offroad competition) and makes us(our team) an offer.
They sponsor us with gas and oil mix.If we finish the ISDT we get a nice lump sum of money.(we all where hungry amateurs).
If we got a Silver or Goldmedall we would get even a lot more money and maybe a contract for the following season.
So whats the catch we where asking.
Well the mix will be 50-1.(oh shi......)
If we would have a oil related failure,we would get a brand new motorcycle of the same model.
After a team member meeting and discussion we decided to go for it.
All bikes got filled with there mix and we wend out for carb testing and tuning.After done that,we made a full power test in the mountins(ALPS).There was one thing right away we realised,the bikes startet very easy,had a crisp and healthy sound,and did not smoke.
Result after 6 days we all finished and I had my very first GOLD.
In 1967 I moved to Canada and in1970 a Canadian friend and distributor visited me in my shop to show me this new oil he was interestet to import,but,,,,he wantet me to test my bike first,...because it has to be mixed 100-1.Yes it was OPTIMOL oil.It was a little shock because even now we where using oil mixes 50-1 but 100-1.???Well it worked and I never looked back.
Most important.Carb.set up.Constant gasoline and oil mix with the same make.
(http://img62.imageshack.us/img62/2509/3buntesallerlei.jpg) (http://img62.imageshack.us/i/3buntesallerlei.jpg/)
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hot dog! an oil thread. where's the personal attacks?
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No personal attacks!! Please!! :o :o :o :o :o
Really choosing the oil and ratio for a two-stroke is like picking a wife (or significant other) You like some and you may not like others, but there is no perfect one that everyone has to have!!
When it comes to oil and ratios, smile, relax, experiment and use what works for you!
On another note, I find Helmut's stories extremely informative and interesting, please keep them coming.
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admin, i'm just kidding. every oil thread i've ever seen on the internet turns personal. i hope this place is different because honestly someone could run canolla oil for all i care.
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hot dog! an oil thread. where's the personal attacks?
Since you asked,I'll start.I wouldn't give a mouldy hotdog for your your oil theories admiral-hee,hee.Hows that.Anyhoo,years ago MacCulloch,of chainsaw fame at the time,did extensive testing and found to best power/performance to be had at a ratio of 12:1.Mind you,oils today are obviously different but I always thought that was interesting.
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admin, i'm just kidding. every oil thread i've ever seen on the internet turns personal. i hope this place is different because honestly someone could run canolla oil for all i care.
Admiral, I knew that you were joking.... just having some fun!
What about popcorn scented oil?? Mmmmm Yummmy! ;D ;D
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hot dog! an oil thread. where's the personal attacks?
Since you asked,I'll start.I wouldn't give a mouldy hotdog for your your oil theories admiral-hee,hee.Hows that.Anyhoo,years ago MacCulloch,of chainsaw fame at the time,did extensive testing and found to best power/performance to be had at a ratio of 12:1.Mind you,oils today are obviously different but I always thought that was interesting.
oh yeah? :P well just to horrify the oil zealots, i will tell you that i almost always run a "witch's brew" of 2T oil. i routinely blend different brands together. a few years ago when the distributor Motorcycle Stuff was in it's final year of operation, i was given a sample 12L case of Repsol moto2T oil. they had just started carring the oil line. the stuff was clear like baby oil. you couldn't tell at a glance whether you had a gallon of premix or a gallon of straight gas. so i got a clean 5 gal. bucket and emptied the Repsol bottles into it then scoured the shop for half used bottles of any 2T oils i could find. i mixed in some Klotz R-50, Honda HP-2, Motul 800, Mobil 2T,and Redline. those oils were red and blue so they made purple and dyed the clear Repsol purple. i have ran that stuff through my mx bikes, both my outboard motors, chain saws, and weed wackers. i'm still using it up.
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Hello everyone. I'm new here, and just thought I would start with a bang! This is my personal take on mix ratios.
Pre-Mix 101
Looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded and hard-headed on the subject, but I'll put in my $.02 here anyway.
Anyone that believes that spooge and plug fouling are caused by too much oil in the mix is flat out wrong. If you know how to jet, you can run any amount of oil you choose, and have absolutely zero spooge.
There is a prevailing myth that less oil is better. This simply isn't the case. While there isn't a magic "one-size-fits-all" mix ratio, and it is possible to use too much oil for your conditions, generally speaking, more oil is better, within certain limitations.
When an engine is jetted too rich, the excess fuel leeches heat from the combustion process, causing the combustion chamber temperatures to be too low to effectively burn the oil, or even completely burn all of the fuel. The result is spooge and deposits. The spooge is nothing more than unburned fuel and oil passing out the exhaust.
If you have a spooge problem, you have a jetting problem. You don't get rid of the spooge by reducing the oil, you get rid of it by fixing the jetting. Correct jetting will produce an air/fuel ratio of about 14:1, which will produce combustion temperatures in the 6000F range and exhaust temperatures in the 1200F range. This will provide sufficient heat to consume the premix oil.
The same goes for plug fouling. Rich jetting does two things. First, it promotes incomplete combustion of the fuel and the oil due to reduced combustion temperatures. The incomplete combustion of the fuel and oil promotes deposit formation inside the engine. Second, rich jetting reduces the combustion temperatures, which in turn reduces the engines ability to burn off deposits. Combine increased deposit formation with reduced ability to burn off those deposits, and what do you get? Spooge and plug fouling.
You don't choose a mix ratio based on "spooge" or plug fouling, you choose the ratio based on the amount of oil your engine needs to provide sufficient protection and adequate ring seal. The common misconception is that mix ratios are "one-size-fits-all", when in fact nothing could be farther from the truth.The amount of oil that is correct for one rider on his bike may not be enough oil for another rider/bike, or it may be too much oil. It all depends on engine displacement, riding style, and how hard you push the engine. A trail rider on a 500 that never reams the bike out is probably fine on a diet of 50:1, where a super-fast up-and-coming young future pro that screams an 85 'till the dogs howl the entire time he's on the track might not get a full day of racing out of an engine on less than 30:1. Your engine's oil needs are determined by displacement, rev range, and the loads you put on your engine.
When you shut your engine down and let it sit, much of the oil drains down into the crankcase and forms a puddle in the bottom. The depth of this puddle is your indicator of whether you are running the correct amount of oil for your engine's needs. Ideally, you want this puddle to be between 1/8 and 1/4 inch. If it's less, you need more oil in your mix. If it's more, you are running more oil than you need for your conditions.
With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 32:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.
When I was much younger and a lot faster, 32:1 wasn't enough oil for my conditions. I needed 26:1 to have enough oil. And I have run as much as 18:1 with no spooge or plug fouling issues.
To understand why the mix ratio is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine. The oil mist is distributed throughout the engine by the spinning crankshaft and the moving air currents to coat all the internal surfaces.
People believe that the oil just rushes right through a two-stroke along with the fuel, but that just isn't so. It can take 90 minutes or more for the oil migration through a two-stroke to result in a complete oil exchange on a slow trail ride, and even as much as 5 minutes for a full-throttle 20 minute moto.
The oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1 in a small-bore engine, you simply can't jet very lean without risking a seized engine due to oil starvation.
One small point. No one ever broke an engine by using too much oil.
Now we come to the issue of ring seal. Simply put, the rings alone can not effectively seal the cylinder. They also need oil to provide a complete seal against the bore surface. And up to a point, more oil will provide a better seal.
I have run Dyno tests on this subject, as a school project in Tech School. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.
Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.
The bottom line? Choose a mix ratio that is adequate for your needs, and jet accordingly. You don't fix plug fouling and spooge by adjusting your mix ratio.[/color
This is an interesting read that also supports my "more oil is better" claim.
http://www.bridgestonemotorcycle.com (http://www.bridgestonemotorcycle.com)...oilpremix6.pdf
And this is a good article as well:
http://www.maximausa.com/technical/l...summer2001.pdf (http://www.maximausa.com/technical/l...summer2001.pdf)
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Hello everyone. I'm new here, and just thought I would start with a bang! This is my personal take on mix ratios.
Pre-Mix 101
Looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded and hard-headed on the subject, but I'll put in my $.02 here anyway.
Anyone that believes that spooge and plug fouling are caused by too much oil in the mix is flat out wrong. If you know how to jet, you can run any amount of oil you choose, and have absolutely zero spooge.
There is a prevailing myth that less oil is better. This simply isn't the case. While there isn't a magic "one-size-fits-all" mix ratio, and it is possible to use too much oil for your conditions, generally speaking, more oil is better, within certain limitations.
When an engine is jetted too rich, the excess fuel leeches heat from the combustion process, causing the combustion chamber temperatures to be too low to effectively burn the oil, or even completely burn all of the fuel. The result is spooge and deposits. The spooge is nothing more than unburned fuel and oil passing out the exhaust.
If you have a spooge problem, you have a jetting problem. You don't get rid of the spooge by reducing the oil, you get rid of it by fixing the jetting. Correct jetting will produce an air/fuel ratio of about 14:1, which will produce combustion temperatures in the 6000F range and exhaust temperatures in the 1200F range. This will provide sufficient heat to consume the premix oil.
The same goes for plug fouling. Rich jetting does two things. First, it promotes incomplete combustion of the fuel and the oil due to reduced combustion temperatures. The incomplete combustion of the fuel and oil promotes deposit formation inside the engine. Second, rich jetting reduces the combustion temperatures, which in turn reduces the engines ability to burn off deposits. Combine increased deposit formation with reduced ability to burn off those deposits, and what do you get? Spooge and plug fouling.
You don't choose a mix ratio based on "spooge" or plug fouling, you choose the ratio based on the amount of oil your engine needs to provide sufficient protection and adequate ring seal. The common misconception is that mix ratios are "one-size-fits-all", when in fact nothing could be farther from the truth.The amount of oil that is correct for one rider on his bike may not be enough oil for another rider/bike, or it may be too much oil. It all depends on engine displacement, riding style, and how hard you push the engine. A trail rider on a 500 that never reams the bike out is probably fine on a diet of 50:1, where a super-fast up-and-coming young future pro that screams an 85 'till the dogs howl the entire time he's on the track might not get a full day of racing out of an engine on less than 30:1. Your engine's oil needs are determined by displacement, rev range, and the loads you put on your engine.
When you shut your engine down and let it sit, much of the oil drains down into the crankcase and forms a puddle in the bottom. The depth of this puddle is your indicator of whether you are running the correct amount of oil for your engine's needs. Ideally, you want this puddle to be between 1/8 and 1/4 inch. If it's less, you need more oil in your mix. If it's more, you are running more oil than you need for your conditions.
With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 32:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.
When I was much younger and a lot faster, 32:1 wasn't enough oil for my conditions. I needed 26:1 to have enough oil. And I have run as much as 18:1 with no spooge or plug fouling issues.
To understand why the mix ratio is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine. The oil mist is distributed throughout the engine by the spinning crankshaft and the moving air currents to coat all the internal surfaces.
People believe that the oil just rushes right through a two-stroke along with the fuel, but that just isn't so. It can take 90 minutes or more for the oil migration through a two-stroke to result in a complete oil exchange on a slow trail ride, and even as much as 5 minutes for a full-throttle 20 minute moto.
The oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1 in a small-bore engine, you simply can't jet very lean without risking a seized engine due to oil starvation.
One small point. No one ever broke an engine by using too much oil.
Now we come to the issue of ring seal. Simply put, the rings alone can not effectively seal the cylinder. They also need oil to provide a complete seal against the bore surface. And up to a point, more oil will provide a better seal.
I have run Dyno tests on this subject, as a school project in Tech School. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.
Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.
The bottom line? Choose a mix ratio that is adequate for your needs, and jet accordingly. You don't fix plug fouling and spooge by adjusting your mix ratio.[/color
This is an interesting read that also supports my "more oil is better" claim.
http://www.bridgestonemotorcycle.com (http://www.bridgestonemotorcycle.com)...oilpremix6.pdf
And this is a good article as well:
http://www.maximausa.com/technical/l...summer2001.pdf (http://www.maximausa.com/technical/l...summer2001.pdf)
WORD!
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I thought your other post was good!! Damn, this is the best explanation of oil mix ratios that I have ever read.
Thank you.
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Like I said before,,
It is just like religion.You never come to a 100 % conclusion.
Fact for me is:
Since the early 70s when MY oil came to Canada,I have used it in all my Vintage and Modern bikes at a mix rate of 100-1 in MX in HS in Enduros in ISDTs(and that is 6 days brutal on the engine) and never ever had a failure.Never a piston sizer,nothing.
That MORE OIL (look what Hydraulic is doing) show more power on a DYNO is well known.But DYNO and real life is a lot of difference.
Piston-Pistonring and modern cylinder material(plating etcetera)have reached a quality which gives factorys (like KTM) which are very carefull what they suggesting) a recommendet oil ratio from(always depend what oil) from up to 80 to 1.
I always tought my customers to mix what the bottle says.And have the carb jetted accordingly.After that,stick to the same brand of OIL and even Gasoline .
Otherwise,...whatever makes you happy. ;D ;)
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Like I said before,,
It is just like religion.You never come to a 100 % conclusion.
Fact for me is:
Since the early 70s when MY oil came to Canada,I have used it in all my Vintage and Modern bikes at a mix rate of 100-1 in MX in HS in Enduros in ISDTs(and that is 6 days brutal on the engine) and never ever had a failure.Never a piston sizer,nothing.
That MORE OIL (look what Hydraulic is doing) show more power on a DYNO is well known.But DYNO and real life is a lot of difference.
Piston-Pistonring and modern cylinder material(plating etcetera)have reached a quality which gives factorys (like KTM) which are very carefull what they suggesting) a recommendet oil ratio from(always depend what oil) from up to 80 to 1.
I always tought my customers to mix what the bottle says.And have the carb jetted accordingly.After that,stick to the same brand of OIL and even Gasoline .
Otherwise,...whatever makes you happy. ;D ;)
Starting lines and trail heads all over the country are filled with bikes running anything from 20:1 to 100:1, with anything from 10W-40 engine oil to Weedeater oil, and most of them live to play another day. That doesn't neccessarily mean it's the best thing for your engine, it just means that modern engine design and metalurgy has gotten so good that the engines are more tolerant than ever to "less-than-optimal" owner practices. But you're right, it's like a religion, and most people will run what they believe to be best. And I'm good with that! If it works for you, that's great.
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Chokey something very similar to Pre-mix 101 was originaly posted by a fellow called 'Spanky' ??
Have always will always use a castor/synthetic blend at 18-20:1, oils have not realy changed nor have crankpins and needle rollers.Nothing provides the same protection as castor, that begins to work when sythetic /mineral cries enough.
Yes 'spooge' is a indication of incorrect jetting and ignition. GP125's blow a whiff of smoke when the light goes green, that's it in 45mins of racing.
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Chokey something very similar to Pre-mix 101 was originaly posted by a fellow called 'Spanky' ??
And that would be me. I also go by Spanky on some forums, although none of them are very active anymore.
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I for the most part agree with all of this. Spooge can be hard to avoid when you have large temperature swings unless you are willing to constantly reject and with the aluminum framed bikes that can be a real PITA.
I've noticed that spark arrestors will spooge more than silencers. While it is possible that is just a jetting issue I suspect that the arrestor lowers the exit temp of the exhaust gas and causes the spooge to drop out of suspension.
My experience has been that lower rod end bearings fail first from a lack of 2T oil.
Hello everyone. I'm new here, and just thought I would start with a bang! This is my personal take on mix ratios.
Pre-Mix 101
Looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded and hard-headed on the subject, but I'll put in my $.02 here anyway.
Anyone that believes that spooge and plug fouling are caused by too much oil in the mix is flat out wrong. If you know how to jet, you can run any amount of oil you choose, and have absolutely zero spooge.
There is a prevailing myth that less oil is better. This simply isn't the case. While there isn't a magic "one-size-fits-all" mix ratio, and it is possible to use too much oil for your conditions, generally speaking, more oil is better, within certain limitations.
When an engine is jetted too rich, the excess fuel leeches heat from the combustion process, causing the combustion chamber temperatures to be too low to effectively burn the oil, or even completely burn all of the fuel. The result is spooge and deposits. The spooge is nothing more than unburned fuel and oil passing out the exhaust.
If you have a spooge problem, you have a jetting problem. You don't get rid of the spooge by reducing the oil, you get rid of it by fixing the jetting. Correct jetting will produce an air/fuel ratio of about 14:1, which will produce combustion temperatures in the 6000F range and exhaust temperatures in the 1200F range. This will provide sufficient heat to consume the premix oil.
The same goes for plug fouling. Rich jetting does two things. First, it promotes incomplete combustion of the fuel and the oil due to reduced combustion temperatures. The incomplete combustion of the fuel and oil promotes deposit formation inside the engine. Second, rich jetting reduces the combustion temperatures, which in turn reduces the engines ability to burn off deposits. Combine increased deposit formation with reduced ability to burn off those deposits, and what do you get? Spooge and plug fouling.
You don't choose a mix ratio based on "spooge" or plug fouling, you choose the ratio based on the amount of oil your engine needs to provide sufficient protection and adequate ring seal. The common misconception is that mix ratios are "one-size-fits-all", when in fact nothing could be farther from the truth.The amount of oil that is correct for one rider on his bike may not be enough oil for another rider/bike, or it may be too much oil. It all depends on engine displacement, riding style, and how hard you push the engine. A trail rider on a 500 that never reams the bike out is probably fine on a diet of 50:1, where a super-fast up-and-coming young future pro that screams an 85 'till the dogs howl the entire time he's on the track might not get a full day of racing out of an engine on less than 30:1. Your engine's oil needs are determined by displacement, rev range, and the loads you put on your engine.
When you shut your engine down and let it sit, much of the oil drains down into the crankcase and forms a puddle in the bottom. The depth of this puddle is your indicator of whether you are running the correct amount of oil for your engine's needs. Ideally, you want this puddle to be between 1/8 and 1/4 inch. If it's less, you need more oil in your mix. If it's more, you are running more oil than you need for your conditions.
With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 32:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.
When I was much younger and a lot faster, 32:1 wasn't enough oil for my conditions. I needed 26:1 to have enough oil. And I have run as much as 18:1 with no spooge or plug fouling issues.
To understand why the mix ratio is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine. The oil mist is distributed throughout the engine by the spinning crankshaft and the moving air currents to coat all the internal surfaces.
People believe that the oil just rushes right through a two-stroke along with the fuel, but that just isn't so. It can take 90 minutes or more for the oil migration through a two-stroke to result in a complete oil exchange on a slow trail ride, and even as much as 5 minutes for a full-throttle 20 minute moto.
The oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1 in a small-bore engine, you simply can't jet very lean without risking a seized engine due to oil starvation.
One small point. No one ever broke an engine by using too much oil.
Now we come to the issue of ring seal. Simply put, the rings alone can not effectively seal the cylinder. They also need oil to provide a complete seal against the bore surface. And up to a point, more oil will provide a better seal.
I have run Dyno tests on this subject, as a school project in Tech School. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.
Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.
The bottom line? Choose a mix ratio that is adequate for your needs, and jet accordingly. You don't fix plug fouling and spooge by adjusting your mix ratio.[/color
This is an interesting read that also supports my "more oil is better" claim.
http://www.bridgestonemotorcycle.com (http://www.bridgestonemotorcycle.com)...oilpremix6.pdf
And this is a good article as well:
http://www.maximausa.com/technical/l...summer2001.pdf (http://www.maximausa.com/technical/l...summer2001.pdf)
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My experience has been that lower rod end bearings fail first from a lack of 2T oil.
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Exactly so.In my case though,I'm 40:1 for tight slow woods races/rides and between 25/30:1 for track use or more wide open running.
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Thank you very much.