Oil to Gas - First, Make It Last

The question - I own a 87 banshee and I was wondering what kind of mixture you run. The manual says 20:1 - that is 32 oz of oil to 5 gallons right? Also my quad smokes a lot on start up and when I pin the throttle it gives out a lot of smoke. The engine is not worn, it was recently rebuilt. The engine runs good too, no problems except the smoke. I think it is just running to rich. How do I correct this. I used to have a KX 125 but I am sort of confused on how to adjust this bike because of the twin carbs.

The response - Thirty-two ounces of oil to 5 gallons of gas is a lot of oil. It probably is running very rich - on oil. Don't confuse that with the mixture of fuel to air because it's a different thing. But you surely can improve on that oil ratio. If you've been running that mixture (20:1) and are going to switch to a leaner oil to gas ratio, you will also need to lean out the midrange and main jetting as well since more fuel will be passing through the jets - the high oil to gas ratio displaces much fuel - in order to get your motor performance back. Actually it should be improved overall. Recently I wrote about oil ratios during break in - though it had to do with additional oil in the gas during break in only, I think you'll find some of it pertains to your situation as well, though the jetting recommendations would be the opposite of what you need to do. I have cut and pasted the question and response to it below.

I have heard a lot of different points on the pre-mix during brake in. I am also going to be faced with this question soon. Does adding extra oil in the mix protect the cylinder and piston more, or will the extra cooling loss do more damage? I would sure like to here from the Gurus on this. Also got to figure into the equation that a Blaster is a air cooled engine.

If you add more oil to the gas during break in - it WILL lean out the mixture of fuel to air throughout the whole rpm operating range. You must compensate for it by richening up all mixture settings. Drop the clip one or two notches (to raise the needle), increase the size of the main jet a couple of sizes and adjust the idle speed air screw to let the motor idle at its fastest rpm - then turn the idle speed down. You could skip all of this by just keeping the same amount of oil in the gas as you normally run. Once your new top end is broken in - in a tank full of gas or two - you will need to change the jetting again. That is - when you change back to the amount of oil you used to use.

If you get the opportunity to take apart an engine very often you may notice that the bottom end of a two stroke almost always has a substantial amount of oil laying in the cases. Even in engines that have been run at leaner oil to gas ratios (50:1 to 100:1) there is plenty of oil. The other internal parts of the engine also are well coated wet with oil. It doesn't matter if the motor is air cooled or liquid cooled - the internals of the engine are still coated. Much of this oil may accumulate at idle and during periods of low rpm running. Once you get the motor spinning faster and it is under load, that extra oil in the case may finally have a chance to become suspended again in the fuel and air mixture and perhaps be burned.

Many people will rev their engine to clear that oil (that plume of smoke they get at startup or after idle) and refer to it as "cleaning out" the engine. And that is exactly what is happening. That oil - which has become separated from the fuel has gathered in the cases and is standing by waiting for some serious turbulence to get it up the transfer ports and into the cylinder where it can finally be burned. Too much oil in the gas can lead to additional problems like carbon deposits on the piston crown and cylinder head, sticky rings, fouled plugs and wet drippy black gunk (unburned oil) coming out of the joints of the exhaust system.

It is probably best to avoid sustained periods of idle, or very low rpm running under no load. It is also probably better to choose a lower gear (for instance 3rd at 5000 rpm instead of 4th at 3800 rpm) and let the motor spin faster when driving at slower speeds since there in less likely a chance of the oil not finding its way to the combustion chamber. It is my opinion that if you use top quality oils (synthetics are the best) you are only throwing away money and making more smoke by running more oil through the engine than it needs. I have had good luck by always using the same oil to gas ratio and the same oil brand.

Rick

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