Wideband Kadron Tuning

UK Luke 72 · Posted: Thu Apr 05, 2012 3:18 pm Post subject:

My accel pump squirts if you only look at the throttle and I'm running a good svda so any hesitation is unlikely, I appreciate the eff being less but the difference in rich afr to lean at cruise isn't pennies over here! £1.50 per litre!!!

Btw... Where are the idle jets Embarassed

andk5591 · Posted: Thu Apr 05, 2012 3:52 pm Post subject:

Idle jets are on the right side of the carb body - abuty 1/2 way down - look for a brass 8mm nut and thats it.
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UK Luke 72 · Posted: Wed Apr 11, 2012 11:51 am Post subject:

right, I've been having a play. I've got 130's and 55 idles in at the minute. here's a quick couple of videos Rolling Eyes

Here's a steady cruise at 40mph

Image may have been reduced in size. Click image to view fullscreen.

and here's idle and takeoff.

I'm thinking i need to come down on the idles a fair bit first then the mains may come about right.

Am I heading the right way?

Thanks!!!

UK Luke 72 · Posted: Thu Apr 12, 2012 3:59 am Post subject:

Anybody?!

modok · Posted: Thu Apr 12, 2012 7:24 pm Post subject:

If your asking which direction to try first, I think it definitely would be to try a step leaner, and see how it reacts

Tuning carbs sometimes takes a few days, either you've been thinking about it for months or you left out a lot of details. I like details

UK Luke 72 · Posted: Thu Apr 12, 2012 10:36 pm Post subject:

Ok what info do you need modok?

modok · Posted: Fri Apr 13, 2012 12:47 am Post subject:

Just giving you a hard time bro
Would be good to say what combinations of jets you have tried and how it ran with this and that, that wideband is a very useful tool but what you can do is still limited by what the engine will tolerate.
You'll never know the limits if you don't "provoke" it a little Wink

UK Luke 72 · Posted: Fri Apr 13, 2012 12:19 pm Post subject:

Gonna drop some 125's in later on... See what she thinks to that.

I'm amazed at just how little the mixture screw does, I thought it proportionally adjusted the afr across the idles and mains. By the looks of things it only SLIGHTLY impacts them but really leans out the idle... I think 20:1 is to lean though!

UK Luke 72 · Posted: Fri Apr 13, 2012 1:54 pm Post subject:

125 mains
55 idles

13:1 WOT
12.5:1 cruise
18:1 idle

Gotta get some 50 idles!!!

[email protected] · Posted: Fri Apr 13, 2012 2:01 pm Post subject:

the idle mixture screw adjusts idle mixture ONLY. Light throttle A/F should be adjusted with the idle JET (not the mixture screw). Make changes "2.5" at a time, not 5. 5 is too much.
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UK Luke 72 · Posted: Fri Apr 13, 2012 2:09 pm Post subject:

I'm not blessed with an abundance of jets this side of the pond though John :/
I've got my hands on
1x 127.5,
4x 130's,
2x 125's,

3x 55's,
2x 60's.

From what I can gather though PICT series carbs didn't come with 50 idles Sad

Thanks for your input John!

mharney · Samba Member Joined: June 01, 2002 Posts: 8351

The more the throttles are open at idle, the less the mixture screws will do to affect idle quality. This is even more the case when you have a balance tube.

UK Luke 72 · Posted: Fri Apr 13, 2012 2:36 pm Post subject:

I'm not sure what you mean...
I have a balance tube fitted.

UK Luke 72 · Posted: Sun Apr 15, 2012 11:05 am Post subject:

Didn't realize you sold jets John...

Can you help me out?!

mharney · Samba Member Joined: June 01, 2002 Posts: 8351

Look at how the idle speed works. The screw positions the throttle plate. More open means more air. It also means you are exposing the progression holes that supply fuel in low throttle conditions. Balance tubes tend to require that the throttle is open MORE for the same idle speed than setups that don't use the balance tube. This means that more fuel is being delivered by the progression circuit and less by the mixture screw port, and the effects of the mixture screw become less definitive.

UK Luke 72 · Posted: Sun Apr 15, 2012 11:57 am Post subject:

So are balance tubes even a good idea for a DD?

modok · Posted: Sun Apr 15, 2012 12:32 pm Post subject:

The balance tube will make it run more evenly on all four cylinders in lower rpm part throttle conditions, which can be good

With more radical cams the idle may be better without the balance tube, symmetry be dammed

UK Luke 72 · Posted: Sun Apr 15, 2012 12:42 pm Post subject:

Thanks modok, my cam is rather mild so I'll keep the balance tube!

UK Luke 72 · Posted: Tue Apr 17, 2012 11:23 am Post subject:

OK so an update...
125 mains
50 idles

13:1 WOT
17:1 idle
14:1 cruise

should i go down another on the idle?

also...
check out my plug colour after 5 minutes of idle
the one on the left was cool to the touch, the one on the right was almost too hot to hold. is this just due to the odd idle characteristics of Kads?
Image may have been reduced in size. Click image to view fullscreen.

and...
these are the jets I'm using, out of 30 PICT3 carbs, they're slightly different but from what i can gather they're identical if you get me...
Image may have been reduced in size. Click image to view fullscreen.

can you see any potential issues here?

much appreciated!

modok · Posted: Tue Apr 17, 2012 11:43 am Post subject:

If it still drives ok with those idles looks like you could try a step smaller yet.
Reading 17 at idle is pretty lean, did you re-adjust the idle mix screws since changing the jets?

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