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28:1 mixing ratio?

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32:1. You don't need all that oil.
Without knowing how hard he rides, you can't possibly say that with any degree of accuracy.

yamaha_rulez_125, as long as you know how to jet properly, you can run as much oil as you want, with no spooge or fouling problems. I ran 26:1 in my 250s for years, but now that I'm old and slow, 32:1 gives me enough oil for my engine's needs.

High-revving engines like 85s and 125s need more oil than larger, slower revving engines. And if you keep it pinned and screaming all the time, you need higher oil concentrations than a trail rider that rarely reams the snot out of the engine. There is only one way to know for sure if you are running the correct amount of oil for your needs. When you pull the top-end off for a rebuild, measure the residual build-up in the crankcase. Stick a thin wooden dowel between the crank halves, until it touches the bottom of the crankcase. Pull it out, and look at the oil level like a dipstick. If there is enough oil to cover 1/8" to 1/4" of the end of the stick, then you are running the correct amount of oil for your needs.

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Without knowing how hard he rides, you can't possibly say that with any degree of accuracy.

yeah, but you don't know what oil he's using. :thumbsup:

Of course, if he's using crap oil, he might need 28:1. If he is running castor or ester, I gurantee you, you'll never need more than 32:1. If he does, his name might as well be James Stewart.

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Hes talking about how hard he rides. And Chokey, you are dead on, its about how hard you ride and jetting.

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Not that it means anything for a YZ, but the recommended ratio for a 125SX is 40-60:1. And FYI, castor and ester based oils usually have 3-4 times the film strength of petroleum, or syn/ petroleum based oils.

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Without knowing how hard he rides, you can't possibly say that with any degree of accuracy.

yamaha_rulez_125, as long as you know how to jet properly, you can run as much oil as you want, with no spooge or fouling problems. I ran 26:1 in my 250s for years, but now that I'm old and slow, 32:1 gives me enough oil for my engine's needs.

High-revving engines like 85s and 125s need more oil than larger, slower revving engines. And if you keep it pinned and screaming all the time, you need higher oil concentrations than a trail rider that rarely reams the snot out of the engine. There is only one way to know for sure if you are running the correct amount of oil for your needs. When you pull the top-end off for a rebuild, measure the residual build-up in the crankcase. Stick a thin wooden dowel between the crank halves, until it touches the bottom of the crankcase. Pull it out, and look at the oil level like a dipstick. If there is enough oil to cover 1/8" to 1/4" of the end of the stick, then you are running the correct amount of oil for your needs.

100% correct!!! Listen to this post, because this is your correct answer.

I personally run 26:1 caster 927

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Yea I definately agree with Chokey's post. ANyways, I use Castrol TTS. My bike is brand spanking new. So would I be safe to say 28:1 would be good to run for stock jetted bikes?

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Yea I definately agree with Chokey's post. ANyways, I use Castrol TTS. My bike is brand spanking new. So would I be safe to say 28:1 would be good to run for stock jetted bikes?

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i believe yamaha reccomends 30:1. stock jetting in california would be fine there, especially if you wrap it out.

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Not that it means anything for a YZ, but the recommended ratio for a 125SX is 40-60:1. And FYI, castor and ester based oils usually have 3-4 times the film strength of petroleum, or syn/ petroleum based oils.

Oil is cheap insirance IMHO. I would never run 60:1 on anything I had to pay for parts on.

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aright one more question guys..if i ran 32:1 id have to mix 8 oz of oil...if i ran 30:1 id have to use 8.5333333 oz of oil which is rounded to 8.5...so would the measurements have to be dead on or will it make much of a difference?

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So would I be safe to say 28:1 would be good to run for stock jetted bikes?

If you ride your bike hard, and rev the snot out of it all the time, then 28:1 will be fine. Do you need that much oil? Maybe, maybe not, it all depends on how you ride. Like I said, the only way to know for sure is to test. Until it's time for a tear-down so that you can check the level of oil in the crankcase, better to run too much oil than not enough. I can't tell you how many engines I've replaced lower-ends in that had nearly dry crankcases when I took them apart. People assume that oil ratios are "one-size-fits-all", and that just isn't the case. And I would never even consider running some of the more ridiculous ratios that I hear people use, like 50 and 60:1, unless I was riding a 500 two-stroke. 500s only spin 6500-7000 rpm, and most riders can't hang on to them long enough to reach even those revs. Smaller engines just rev too high to live long on ratios that lean, unless they get ridden fairly easy. 250s easily rev to 9500-10,000 rpm, and 125s turn as much as 12,000. 85s can turn 14,000 rpm.

Whether the stock jetting is correct or not is a seperate issue and has nothing to do with how much oil you run. Regardless of what mix ratio you choose, you may still have to make some jetting changes. Stock jetting is rarely perfect, even under the "ideal" conditions that the bike was jetted for from the factory (sea level, 75 degrees, 50% humidity). When riding in different conditions, you need different jetting.

Here's a few words to live by:

Pre-mix 101

OK, 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 on the subject, but I'll put in my $.02 here anyway.

There is a prevailing myth that less oil is better, and that the oil in the fuel is what lubricates the engine. Both are wrong. The engine is lubricated by the residual oil that builds up in the crankcase. All the oil in the fuel does is replenish this oil.

The best way to determine if you are running enough oil is to check the level of the residual oil in the crankcase. If the ratio you run leaves enough residual oil in the crankcase to cover about 1/8" of the bottom of the crank wheels, then you are fine. If you don't have that much residual oil in your crankcase when you pull the top-end off, you aren't running enough oil for your riding style and 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 26:1 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.

To understand why the residual oil 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, but it must get to the parts to lubricate them. The way it gets to the bearings and onto the cylinder is by being thrown around by the spinning crankshaft, and being distributed through the engine by the air currents moving through the crankcase. The main bearings are lubed by some of this oil dripping down through tiny "drip passages" in the cases above the bearing pockets.

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, you simply can't jet very lean without risking a seized engine due to oil starvation.

With the high oil concentrations that I use, I tend to get far more life from my cranks and rings than most of my friends that run leaner oil ratios. The high oil content also produces better ring sealing, so more of the combustion pressure is retained.

One small point. No one ever broke an engine by using too much oil.

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At 50:1, you simply can't jet very lean without risking a seized engine due to oil starvation.

At 32:1 you have to have tiny jetting to run clean over 85 degrees. I don't like how bikes rev out with small jetting, so I use larger jetting and 50:1.

We could go back and forth all day. The important thing is you give the bike the lubrication it needs one way or another.

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You clearly don't understand jetting at all. There is only one correct combination of jets for any given set of conditions. The idea is to give the engine the correct air/fuel ratio to achieve combustion temperatures in the 1200 degree range. You change jets to find that correct combination. You don't change jets to alter the amount of oil being delivered to your engine. For that, you change the amount of oil in the fuel.

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