UK Karting - Notice Board (General Karting) : Re: Needle change only with jetting software?

Notice Board (General Karting)

Re: Needle change only with jetting software?
Posted by 'John' on 16 Mar 2011 @ 03:54

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JohnJoined: August 2001
Total Posts: 1
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Danlee, you ask about needle settings and mainjet settings together with references to jetting software.

First read my article on this website which hopefully will give you an insight into what’s involved in jetting the Dellorto carb.

But in simple terms what you are trying to achieve is to maintain a perfect air/fuel ratio, now the fuel bit of this equation is your general carb setup and airflow characteristics together with your mainjet and needle profile plus your needle clip position. The air side of the equation is the air density at the moment you are out on the track with the carb setup described above.

As described by Raceinstuctor the atomiser and needle profile/clip position control the fuel flow from Ľ to ľ throttle and the mainjet selection from ľ to full throttle if you are in any way sceptical about this then just remove your mainjet and then start your engine and you will find that it runs OK until it gets to around ľ throttle at which point it then runs very poorly and will eventually stall as at this setting you are running a 266 mainjet.

When testing to find an optimum jetting solution at any particular moment in time then you simply change mainjets, needle profiles and needle clip positions until you hit on the correct solution for the air density at that moment. Now provided you have the time and the air density does not change too much you will eventually hit the correct solution and with more experience you will hit this optimum solution more quickly, but without the reference to air density at the moment you are running your engine then you will always have to go through this process no matter how experienced you are each time you go to the track.

Now there are those on this board and around the paddock that will tell you to only use this range of jets and this needle at this clip position and so on.................. I say that this approach to tuning will always be a compromise however it maybe a compromise which is acceptable to you as it is for others.

The reason I use jetting software is simple, I want to go to the track and spend all of my time on setting up the chassis and tyres and not have to worry about jetting and carb setup. There is much more time to be found with a good chassis and tyre setup.

What am I doing posting at this time of the night? You try sleeping with a bruised spleen and lung LOL

Message Thread:

Needle change only with jetting software? by 'Danlee' (15 Mar 2011 @ 20:24)

Re: Needle change only with jetting software? by 'raceinstructor' (15 Mar 2011 @ 20:41)

Re: Needle change only with jetting software? by 'Danlee' (15 Mar 2011 @ 22:30)

Re: Needle change only with jetting software? by 'John' << You are here!

Re: Needle change only with jetting software? by 'BrianP' (16 Mar 2011 @ 7:54)

Re: Needle change only with jetting software? by 'John' (16 Mar 2011 @ 8:29)

Re: Needle change only with jetting software? by 'BrianP' (16 Mar 2011 @ 8:37)

Re: Needle change only with jetting software? by 'Danlee' (16 Mar 2011 @ 9:24)

Re: Needle change only with jetting software? by 'John' (16 Mar 2011 @ 9:37)

Re: Needle change only with jetting software? by 'KenE' (16 Mar 2011 @ 10:33)

Re: Needle change only with jetting software? by 'pratty' (16 Mar 2011 @ 20:40)

Re: Needle change only with jetting software? by 'John' (16 Mar 2011 @ 21:37)

Re: Needle change only with jetting software? by 'RocketMan46' (16 Mar 2011 @ 21:43)

Re: Needle change only with jetting software? by 'Danlee' (16 Mar 2011 @ 22:34)

Re: Needle Action by 'MikeSimpsonsnr' (17 Mar 2011 @ 18:52)

Re: Needle Action by 'John' (17 Mar 2011 @ 20:42)

Re: Needle Action by 'MikeSimpsonsnr' (18 Mar 2011 @ 6:59)

Re: Needle Action by 'John' (18 Mar 2011 @ 7:31)

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