Needles & mains

[Guest]

How much do the needles affect the mixture?
Do they affect it all through the throttle range?
Is it a better idea to raise the needles or to up the mains?

Now, also what is the usual change in mains, pod, freeer flowing exhaust =what increase?

I have a 110 main, but it is lean now, the needles make no difference, I have tried a 135 main but failed the emissions test.

Oh, this is on the yammy.
Thanks

[mark m]

How much do the needles affect the mixture?

While running on the needle circuit they control it almost completely.

idle - 1/8 throttle = pilot circuit
1/8 - 3/4 throttle = needle circuit
3/4+ throttle = main jets

Do they affect it all through the throttle range?

Both the pilot and needle circuits affect the mixture all the way through the range. This is why it is better to sort your pilot circuit first, then the needles, then the mains last, because the lower circuits affect the ones above them, but not the other way around.

Is it a better idea to raise the needles or to up the mains?

That depends on where your problems are.

have a 110 main, but it is lean now, the needles make no difference, I have tried a 135 main but failed the emissions test.

There is a huge jump between 110 and 135 mains. There must be a happy medium somewhere in between those two...Keep in mind that when you have the bike tuned for best running it will be significantly richer than the stock settings. Gas engines like to be a bit on the rich side, especially our air cooled ones, so you may always have problems with an emissions test when it is tuned for best power and driveability. It depends on how stringent the testing is.


Mark

[mike J]

Not sure if this applys to all carbs, I have played with the needle position and main jets to shift the power delivery. Say for example you have the needle in the 3rd clip and a 120 main. You can sometimes raise the needle and richen the main jet to say a 130 and get a different power band. The plugs will look the same. I have used this before on Mikuni slide carbs. Mike J

[Detman101]

Re: Needles & mains

How much do the needles affect the mixture?
Do they affect it all through the throttle range?
Is it a better idea to raise the needles or to up the mains?

Now, also what is the usual change in mains, pod, freeer flowing exhaust =what increase?

I have a 110 main, but it is lean now, the needles make no difference, I have tried a 135 main but failed the emissions test.

Oh, this is on the yammy.
Thanks

Your 135 main is going to be waaaaay too rich.


With pods and exhaust you are going to need to use either...

115 Mikuni mains with your needles raised as high as they can go.

OR

117.5 Mikuni mains with your needles set in the middle.