Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

Low End Rich Needle Trick:

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Old 08-22-2008, 10:26 PM
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Electriceddie
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Default Low End Rich Needle Trick:

Hi All,

I remember years back someone told me about backing out the low end needle to richen it up quite a bit. The theory was that it gave more top end performance and the engine quit for sure when you wanted it too. Does this sound right to anyone? Is there a an actual correct theory on how this works? How much should it be richened up? Can anyone tell me the proper procedure or is this just an old trick that was used 20 years ago when engines were not as proficient as they are now. I know I did not dream this up..... LOL....


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Old 08-23-2008, 07:36 AM
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daven
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Default RE: Low End Rich Needle Trick:

I've done it both ways in 424, personally I don't see much of a difference. The theory is, if you back the low end needle out as far as it can go, you are allowing the carb to take in more air, hence faster.

There is even a provision in the rules that you can hold the needle in place with commercially available thread locker, epoxy, or other adhesives (read JB weld), and safetied with rubber bands, wire, or plastic ties.

Personally, I like the ability to let you motor idle so you can go around if you don't like your landing approach. Leaving the needle all the way out will cause it to shut off when you bring the throttle to idle.
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Old 08-23-2008, 07:42 AM
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Default RE: Low End Rich Needle Trick:

O yes, it still works!! I take the low end needle out, clean it and the barrel real well, and insert it back in with some thread lock compound. I will only screw it in about 2 turns. What the low end needle does is limit the fuel flow at low speed so that the engine will idle without flooding. Since we don't idle, the exta fuel flow from this gives you a little extra flow overall. Not a whole lot, but every little bit counts! If you look at the Nelsons, Jetts of Profi engines, they do not use a low end needle at all.

Good luck!
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Old 08-23-2008, 08:26 AM
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Default RE: Low End Rich Needle Trick:

I've personaly seen an 80 RPM increase with the needle backed of, and it allways stops when you want it to.
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Old 08-23-2008, 11:01 AM
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Electriceddie
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Default RE: Low End Rich Needle Trick:

Thanks Guys

I knew it was something like that.

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