SX/SXi/SXi Pro Fine Tuning for Factory Pipe

[Balduccimoto]

It's a 93 750SX, dual keihin 40 carbs, new motor, factory pipe, 190 comp. I have it running ok, it just feels too rich. My jets I think are 78 pilot and 145 main. Turns are somewhere 1 1/2 low and 3 1/4 high. Plugs are showing a pretty decent color when I do idle and WOT plug chops. My problem is, when I go WOT I get a bog. It can last anywhere from 2 seconds to 30 seconds before it burns up whatever sits in the case and takes off screaming. Blipping the throttle around gives me pretty good throttle response. Is it the pilot mixture loading it up with fuel and has to be burned out, or is the high way too rich? I don't want to worsen what I got so far.

 

[98SXIPRO]

wish i had water screws so i could get my ski with its new FP on the water and tune mine...(sorry, I'm not much of a help)

 

[jaxrider]

3 1/4 out on the high . try 1 turn out

 

[sxipro02]

3 1/4 out on the high . try 1 turn out

2nd that. 3 1/2 is way too far

 

[kevbo]

Which prop and nozzle.

 

[sxipro02]

Why does that matter lol?

Guessing wrong tread post

 

[Crab]

Why does that matter lol?

Guessing wrong tread post

It matters alot.

 

[sxipro02]

I would get base tuning in before I worry about prop pitch. It sounds fat to me. It its loading up bad enough to cause a 30 sec bough there is just too much fuel in there. That being said tuning adjustments will slightly differ with prop pitch but actually tuning the ski will be the same.

 

[Mark44]

1.Low speed adjuster- to adjust a smooth idle
2.pop off- just of idle to ¼ throttle in conjunction with low speed jet
3.low speed jet-just off idle to 1/3 throttle
4.high speed jet-1/3to ¾ throttle
5.high speed jet ¾ throttle to open throttle

Keep in mind you ADJUST the circuits in THIS ORDER because changing the low speed changes the high speed total fuel delivery.

I agree with sxipro02, don't worry about the impeller till you have the ski tuned and get a good tach. A tiny tach will not work for carb tuning, it doesn't refresh fast enough. PET tach from watcon and your motor will thank you for it.

Mark44

 

[kevbo]

He could have a 21 degree prop in it and be wondering why its sluggish. Just keep twisting the screws.

 

[Balduccimoto]

I am running a 13/19 solas prop with my stock nozzle. It felt like a fine prop on my stock engine. I fattened up the top end because it was a new engine with a new to me factory pipe. I was a little nervous about leaning it out, because when I initially installed the pipe, my bearings gave out when I was tuning! So I will start by leaning out the top end a 1/4 turn at a time. Thanks guys.