I want to make sure I'm understanding needle jets and needles correctly a P-4(247) let in the least amount of air the P-8(247) lets in somewhere in the middle amount of aire and the Q2(247) lets in the most air now for needles the bigger the needle the less fuel it lets in and the smaller the needle more fuel it lets in or is it reversed? I'm trying to figure out more air less fuel

is that for PSI pipes or SLP pipes?[/b]

 

I want to make sure I'm understanding needle jets and needles correctly a P-4(247) let in the least amount of air the P-8(247) lets in somewhere in the middle amount of aire and the Q2(247) lets in the most air now for needles the bigger the needle the less fuel it lets in and the smaller the needle more fuel it lets in or is it reversed? I'm trying to figure out more air less fuel[/b]

The jet needle and needle jet (tube) work together to meter the amount of fuel, mostly in the 3/8 to 3/4 throttle range. As the needle is lifted out of the tube by throttle movement and by the taper design of the needle, more gas is allowed through. The P-4 would have a smaller opening through the tube and as you increase in number size through to, say, Q-2---the orifice size increases about .010" for each increase in number designation. (P-4 being leaner, Q-2 being richer, usually all in even numbers, but not always) The throttle valves, allow the airflow to increase at a given throttle position, mostly from just off idle to about 3/8 throttle position is where this has it's greatest effect. A 1.5 being richer to a 3.5 being leaner.

 

Open the air screw if its fat ! You can open it 2 turns from closed! If still fat close screw to 1/8 turn and go to 25

 

Ya you bet. Everything is crisp and clean until the clutch is engaged and the sled is under a bit of load then it would load up/overfuel before it can get going. I was hoping drilling out the bypass hole as mentioned above would help keep the mixture a little leaner while the throttle is nearly closed.

But I don't want to hit my carbs with a drill bit until I know why the service bulletin called for oversizing to 1mm.

 

At clutch engagement the needles are taking over ! Drop the needles one clip and see what happens... What year is the sled And is it an RMK? I just set a SKS Up with SLP Low RPM pipes 2.0 slides 50 pilots drilled the carbs to 1mm , 6CEY06 needles Q2 tubes and 380 mains runs like a top! I found the slp jetting to be a little funky

 

My question is:

What is drilling the pilot hole to 1mm accomplishing? Leaner or richer on pilot circuit?
Thanks,

 

I really dont think it will make it leaner. I think the idea was because with a larger pilot say a 40 50 or so the hole was to small to flow the larger pilot.. and maybe the larger hole made the pull on the pilot circuit stronger

 

You could try 2.5 or 3.0 slides!! I know back in 96 RMK on my ultra with SLP needles with 30 pilots 1.5 slides it was real blubbery down low ! cut my slide to 2.5 and made a big difference .. I think this 96 sks i just did with the 97 SPX jetting with 2.0 slides is the best setup i have used next to switching mine to XCR 800 carbs