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Mixture screw?

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Hi all ive rejjeted my carb to 160 main and left the stock leak in as it's a 42 anyway, took the mesh from air filter and opened up the airbox, using the red needle on the 5th clip as stated from 0-4000ft witch is my level range, it advises 1 3/4 turns of mixture screw, don't get me wrong it feels punchy'er but theres hesitation down low where there wasn't before?? any ideas? Thank you 

Edited by spenny08

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1 3/4 gets you in the ball park.

 

What you need to do is get the motor fully warmed up, and put a fan on it so it won't over heat.  then:

 

1. Turn the idle down low until it's just running.

 

2. Adjust the fuel screw for the smoothest possible idle.

 

3. Repeat #1 and 2 until you can't any more.

 

4. Raise the idle to 1700 rpms.

 

 If at the end of that process you are less than 1 turn, then you need a larger pilot jet.  If your more then 2 1/4 - 2 1/2, a smaller one.

 

 If it still bogs off idle when slowly rolling the throttle on or pops on decel, then try 1/8 to 1/4 turn out on the fuel screw.

 

Jim.

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1 3/4 gets you in the ball park.

What you need to do is get the motor fully warmed up, and put a fan on it so it won't over heat. then:

1. Turn the idle down low until it's just running.

2. Adjust the fuel screw for the smoothest possible idle.

3. Repeat #1 and 2 until you can't any more.

4. Raise the idle to 1700 rpms.

If at the end of that process you are less than 1 turn, then you need a larger pilot jet. If your more then 2 1/4 - 2 1/2, a smaller one.

If it still bogs off idle when slowly rolling the throttle on or pops on decel, then try 1/8 to 1/4 turn out on the fuel screw.

Jim.

good advice.

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Hey Jim - shouldn't the pilot jet recommendations be in the other way?  If your mixture screw is too far out wouldn't that indicate the need for a larger pilot to move more fuel so you don't need so much adjustment on the mixture?  Or am I reading it cockeyed?

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Hey Jim - shouldn't the pilot jet recommendations be in the other way?  If your mixture screw is too far out wouldn't that indicate the need for a larger pilot to move more fuel so you don't need so much adjustment on the mixture?  Or am I reading it cockeyed?

 

Nope, your absolutely right, I said it backwards. :facepalm:

 

Less than a turn requires a smaller slow jet.   Move than 2 1/2 means a larger one is required.

 

Thanks for the catch!

 

Jim.

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No prob.  Thanks for the tutorial.  I hadn't thought of repeating 1 and 2 until you couldn't do it anymore.

 

For some reason the X low-speed seems to be finicky for a 4T.  I find myself adjusting the mixture as often as I would on a smoker. Fortunately a 1/8th turn always seems to do the trick.  Hey, maybe your repeat 1/2 will end the need for that.

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That's the reason aftermarket mixture screws are so popular.  Even so I find it difficult to reach and adjust, what I need is an extension like the idle speed adjuster.

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That's the reason aftermarket mixture screws are so popular.  Even so I find it difficult to reach and adjust, what I need is an extension like the idle speed adjuster.

 

R&D Flex Jet

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