Makkelijk antwoord *Vincent*...
Dan heb je een mengsel- of afstel probleem.
Bij 2T GP racers komt er slechts een licht plofje rook, voornamelijk tijdens de start.
Als je mengsel en je afstelling goed is, komt er geen olie residu uit de uitlaat.

Anyone who 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.

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.

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, it is possible to use too much oil for your conditions,
generally speaking, more oil is better, but within certain limitations.

When an engine is jetted too rich, the excessive 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.

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 300 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 80cc, 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.


To get 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.

On some previous bikes, 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 ride, or even 5 to 10 minutes on full throttle races.

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.

We 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.
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 2 Stroke, 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.

The bottom line?
Choose a mix ratio that is adequate for your needs, and jet accordingly.
You don't fix Spooge and fouling by adjusting your mix ratio!!!

You don't fix Spooge and fouling by adjusting your mix ratio!!!