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Yammer-Hammer

OBEKQ vs OBEJP

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What the difference between the OBEKQ and OBEJP needles? Which is better for aggressive power? Lets say there both in clip position 4

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I heard the OBEKQ is the most aggresive, i had it in my previous carb and was very happy with the power but i din't test another needle

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The needle, or any other element of the carb that adjusts the mixture one way or other, doesn't create "aggressive power".  Cam design and ignition timing curves do that.  The parts of the carb serve only to make the fuel mix right at different throttle openings, so the bike runs better or worse, depending.

 

There is very little difference between the two needles.  The 5th character is the biggest difference here. That indicates the diameter of the straight, upper portion, which is in effect from just off idle to around 1/4 throttle.  The "P" in this position is a step richer at that throttle position than the needle having a "Q" in the 5th spot.

 

The 4th character tells you how high up the needle the tapered part starts.  The difference between the "J" and the "K" here is that with the clip in the same position on both needles, the needle with the "K" is one half clip position leaner than the "J".

 

So in this case, with both needles clipped in the 4th notch, OBEKQ is slightly richer at 1/8 to 1/4 throttle, and one half step richer at 1/3 to 3/4 throttle than the OBEJP. 

Edited by grayracer513
corrections made
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The needle, or any other element of the carb that adjusts the mixture one way or other, doesn't create "aggressive power". Cam design and ignition timing curves do that. The parts of the carb serve only to make the fuel mix right at different throttle openings, so the bike runs better or worse, depending.

There is very little difference between the two needles. The 5th character is the biggest difference here. That indicates the diameter of the straight, upper portion, which is in effect from just off idle to around 1/4 throttle. The "P" in this position is a step richer at that throttle position than the needle having a "Q" in the 5th spot.

The 4th character tells you how high up the needle the tapered part starts. The difference between the "J" and the "K" here is that with the clip in the same position on both needles, the needle with the "K" is one half clip position leaner than the "J".

So in this case, with both needles clipped in the 4th notch, OBEKQ is slightly richer at 1/8 to 1/4 throttle, and one half step richer at 1/3 to 3/4 throttle than the OBEJP.

. Thanks grey that answered my question and i think i will be throwing the OBEKQ in. When you say ignition timing changes the aggressiveness of the power, it makes me wonder, because i have a 1998 400f CDI and am curious if the map is more grunty than the map on my 2002 426f. CDI?? Do you have any idea grey

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The needle, or any other element of the carb that adjusts the mixture one way or other, doesn't create "aggressive power".  Cam design and ignition timing curves do that.  The parts of the carb serve only to make the fuel mix right at different throttle openings, so the bike runs better or worse, depending.

 

There is very little difference between the two needles.  The 5th character is the biggest difference here. That indicates the diameter of the straight, upper portion, which is in effect from just off idle to around 1/4 throttle.  The "P" in this position is a step richer at that throttle position than the needle having a "Q" in the 5th spot.

 

The 4th character tells you how high up the needle the tapered part starts.  The difference between the "J" and the "K" here is that with the clip in the same position on both needles, the needle with the "K" is one half clip position richer than the "J".

 

So in this case, with both needles clipped in the 4th notch, OBEKQ is slightly richer at 1/8 to 1/4 throttle, but one half step leaner at 1/3 to 3/4 throttle than the OBEJP. 

 

Correct me if I'm wrong here, but think you may have got the taper start point backwards. Isn't the needle with the K one half clip position leaner?   If so then OBEKQ would be leaner from @ closed to 3/4 throttle than OBEJP, when clipped in the 4th notch.  

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Correct me if I'm wrong here, but think you may have got the taper start point backwards. Isn't the needle with the K one half clip position leaner?   If so then OBEKQ would be leaner from @ closed to 3/4 throttle than OBEJP, when clipped in the 4th notch.  

 

You are correct (fixed it).  But remember, it's a one half step difference only, and easily adjusted for by moving the clip. 

 

Between the two, I would guess the EJP would perform better, or at least have less tendency to bog on a sudden throttle opening.

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