3.0ltr ROW 930/10 Question about idle jet...
 

3.0ltr ROW 930/10 Question about idle jet...

First thing first, my set-up:
3.0ltr 930/10 ROW stock freshly rebuilt (compression 9.8:1)
stock cams/stock pistons
standard pointless stock CDI ignition (new rotor/dist./wires)
NGK BP7ES plugs
twin pipe Dansk
1 5/8 headers
Weber 40 IDA3C on phenolic insulators
Idle jet: 60
Air correction: 140
Main jet: 145
Emulsion tube: F26
Venturi: 34mm
3.5 psi of regulated fuel pressure
float levels are absolutely perfect

Symptoms and observations:
-Smells of slight unburned fuel below 3500 rpm.
-Plugs are dark brown/black but not fouled.
-Lower, midrange and top end performance are very good, no dead spot and great transition from idle to full throttle.

When adjusting for Lean Best Idle Mixture, almost all 6 idle mixture screws are all half a turn opened.

Question: If I downsize the idle jet from 60 to 55, this will require the idle adjustment screw to be opened up more to get the same mixture but will provide better fine tuning adjustment to obtain the Lean Best Idle Mixture and get rid of that slightly rich condition on the idle circuit ? Am I wrong with this ?
Thanks in advance for your valued advice.

your thinking is correct
try it , up to 3 turns open is ok, 1.5 open, is the starting pt adjust from there .
If it was 3 turns open I would go down a size . 1 turn open is ok . do you have the long skinny idle mixture screw or the short point , short style is harder to get it right .
The idle air can be helpful as well

I think your main jet is too big , go to 135 or 130
also the main air corrector is too small , try 160 or 155

What is your AFR? Full throttle plug color ?

Ian

Ian, thanks for your inputs, can we interchange the short for long style needle or it is matched with the inner core ?

AFR at 4000 is 12.6, 5500 is at 12.2

what would be the impact to switch from F26 ET to the common F3 ?

More common is the f16 witch is a leaner f then f26 then f11 then f3 , this is in order of richer.
You have nothing in the engine asking for lots of fuel, f16 or f26 is in line , I think.

Lots of trial and error , asking what others run will just screw you up.

Your headers are too large for the build ,

Hire Paul Abbott at performance oriented he is back in biz

Ian

Thanks Ian, will start experimenting as soon as the snow melt over here...