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Fuel/Oil Ratio vs Fuel Air/Ratio
– Fuel/Oil ratio is the amount of oil you are mixing in the gas. It’s in your gas can
– 32:1 is a lot o oil – thick fuel
– 50:1 is less oil – thinner fuel
– 80:1 is even less oil – thinnest fuel
– Pick something that works for you and stick with that. We’ll fine tune the mix with our fuel/air Ratio
– Fuel/Air Ratio is fine tuned inside the carburetor with Jets and needles.
– I’ve got oil running down my silencer and I”m running my bike 32:1. I guess that I’m running it too Rich, right?
– Well yeah, but it’s not because of your oil mix. You are too “rich” but you need to take fuel away from the bike by allowing less of it to enter the cylinder of your bike.
Denser air (more of it) makes your bike fuel lean (less fuel) because now you have more air/pressure but the same amount of fuel
Density altitude is what we are really tuning for.
– Aviation – Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases.
– Air pressure is reduced at higher elevations – Elevation goes up – bike runs ” fuel rich”
– temperature effects our carbs – temp goes up – bike runs “fuel rich”
Pilot Circuit – idle up to about 1/8th
– air screw for fine tuning
– 3/4 of turn out to 2.5 “turns out” is a fine range
– If you have to run the bike at less than 3/4 of a turns out, you will need a bigger pilot jet
– If you need to run it more than 2.5 turns out, then you need a smaller pilot jet
Needle Circuit 1/8th to 3/4 throttle – Where it’s at!
– uses clips to fine tune here
– Moving the clip UP the needle will allow it to drop down further in the carb which restricts fuel (makes it leaner)
– Moving the clip DOWN on the needle keeps the needle higher which add fuel (makes it richer)
Main Circuit 3/4 throttle and up
– there is certainly some cross over here and I’m not saying that it will ONLY effect you at 3/4 throttle, but this is where it mostly comes into play.
How to tune?
– Looking at the spark plug
– Black or wet means there is too much fuel – it’s too cold
– white means that it’s too hot – not enough fuel
– golden brown is right in the sweet spot
– Riding the bike and getting a feel for what is happening – Get it hot before changing anything.
– Find out which jets you have in your bike
– Find a jetting chart for the bike
– Buy the jets and needles that go in the direction you need (more or less fuel)
– Start with the idle jet – is it running smoothly here – bogging or pinging could be a lean condition
– Play with the air screw to tune
– Now swap out the needle or move the needle clip position to either take fuel away or add fuel
– often times for me, I need a leaner needle than stock. Probably 2 steps leaner
– then I fine tune by moving the clip up or down
– Now I got a couple steps leaner with my MAIN jet and by that time the bike is likely running really well.
– sometimes this might require a little fine tuning with the needle clip position
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