whats the truth

[mercury65]

ok i have ben reading for days and hours and the more i read the more it seems that advice is wrong, alot. let me expalin.

9 out of 10 will say to get the main jet on the button first. then the clip then the pilot. ok this is what dont make sence to me. if the pilot never stops adding fuel to the system, meaning from idel to wot . then if you set your main first then find that your pilot is way to rich or lean. you change the pilot, now yor pilot is dead on but you just messed up all the rest of the jetting.

from what i have ben learning should you not set the pilot first?

the neddle has no affect on pilot system, and the main jset has no affect on the pilot system. but the pilot has a affect from idel to wot.

 

so PLEASE can some one set the record stright THANKS

[Male Supremacy]

That is such an awesome question!

 

It's so good that I'll let the masters answer, and I'll read them thoroughly. :biggrin:

 

Seriously, I'd like to know. I've always wondered. Banshee jetting is so tricky. They'll run on jetting that's way off, but when they are on it's amazing what the difference is. Way more so than any 4 stroke I've ridden (including my YFZ)

[Dinner]

Well as far as the jets go and needle go in regards to carb performance, there is basically your pilot jet, air screw, needle and needle clip position, and your main jet.

 

The pilot jet is for start up, idling and well 0-1/8 throttle. The pilot does not add fuel throughout the entire position of the throttle. The air screw is for fine tunning your pilot jet, whether you have to have it at 1/4 turn out or 1.5 turns out. Generally if you are all the way in with the air screw, you are too lean on the pilot. If you have the air screw out more than 2 turns, you are too rich on the pilot jet.

 

The needle is the heart of your carbs performance. The needle begins to work from basically 1/8 throttle, and keeps working until a good 3/4 throttle. There are different style of tapers, lengths and diameters of needles, but you shouldn't have a problem with needles in stock carbs. Your needle clip position is what is important for top performance from 1/8 - 3/4 throttle. Depending on what your engine is "calling" for, you adjust your needle clip.

 

The main jet is for 3/4 to WOT. As the needle comes up with the slide(closer you get to WOT). The needle taper gets smaller, thus allowing the fuel to run through the main jet and into the carb body.

 

Now if you know your quad is in the ball park of jetting. People will usually tune the pilot first, getting it so it is the right size for start up, and also allows no bog off idle once the throttle is beginning to open up (also tune your air screw). Once that is in the right spot, put around and see if you feel the engine is boggy or cutting out from 1/8 to 3/4 throttle. Don't get running WOT, we aren't worried about the Main yet. A good way to tell if your needle clip position is wrong, is when you snap the throttle from 1/8. Does the engine cut out and not pull, or does it just bog? This will tell you whether you need to go up or down on the needle clip. Once you have it running good throughout those areas. Now you can do a WOT run, feel/listen to the engine and also do a plug chop on new plugs.

 

Now this is all coming from my head, so if I'm wrong, correct me.

[Wildcardracing]

Yes, the pilot does flow some at all throttle positions. But it is such a minute amount of fuel that it wouldn't affect your main size unless you were way off on pilot size ie: two or three sizes too big (in which case you may not even be able to start it). The main has more effect on the needle than the needle on the main, this is why it is adjusted first, then needle then pilot. Keep in mind that you should always do one last plug chop to verify your main after all jetting has been dialed in to make sure the other adjustments haven't affected it.

[Dinner]

We just said too different things, I think we are going confuse the man :ermm:

 

With the pilot being 2-3 sizes off, and if he was able to get it started. It would either cut out so bad or bog so bad that he probably wouldn't be able to gain any RPM's. That's why I always thought and tuned my pilot first, that way I can at least be able to get up to the RPM's for tuning your needle and main.

[Wildcardracing]

I only said that about two to three sizes on the pilot statement as an example of how far off your pilot would have to be to affect your main. Most people will be no more than one size off on the pilot. Before the bulk of the jetting even starts they will have to sync thier carbs and will have adjusted the air screws and idle screws (or knob if TORS equiped) to atain a good idle. Once they have the air screws adjusted they will know which way they will have to go on the pilot for final jetting. Agreed, if it's stumbling and bogging in the low end you will tune on your pilot first, but for the final jetting you start with the main and work your way down.

[Snopczynski]

From the mouth of dyno Dave " get your ballpark settings, then adjust main first, then needle, then pilot circuit."

 

From the mouth of Dan at Patriot Racing " Keihin carbs will not draw off the pilot circuit across the board, mikunis will."

[mercury65]

well at the end of the day i fineley got a hold of 1dir racing the place i got the carbs from, they were having new phone system put in. he said pilot, main then neddle. and the reason he gave me was. 1/2 throtle the motor does not use that much fuel so the pilot will efect it, but a little efect on the main because at wot the motor is using alot more fuel and he claimed to have dyno tuned 100's of shee's. he did say to saty a little fat on the pilot for better responce, the motor will have a little extra fuel in it so it will snap right of idel.

 

i did get her done, i now have 42 pilot, CGL middle clip, 155 main 2 1/2 out on the air screw, 2 turns out on the idel screw. it was dead on at 150 in the middle of the day but i put 155 in because the temps drop fast here when the sun goes down, those jets are bigger then i thought i would end up at, at 4500 ft.

 

stock stroke, home port & polish, vitos superstock pistons, noss head 18cc, boysen 2 stage reeds, billet cage, 33pwk, pods, shearer in frames, +2 timing, the sand at st anthony is very soft and bikes heat up quick. so i will keep the timing down to +2..

 

WOW this thing is fast it smokes my stock shee with t5', the power pulls hard way past the toomey's. i dont think i will ever buy a set of toomey's agen. dont think i will ride a stock shee any more eather.

 

THANKS guys.

[mopar1rules]

Yes, the pilot does flow some at all throttle positions. But it is such a minute amount of fuel that it wouldn't affect your main size unless you were way off on pilot size ie: two or three sizes too big (in which case you may not even be able to start it). The main has more effect on the needle than the needle on the main, this is why it is adjusted first, then needle then pilot. Keep in mind that you should always do one last plug chop to verify your main after all jetting has been dialed in to make sure the other adjustments haven't affected it.

 

 

...exactly. i always roll my eyes when people say that the pilot doesn't flow anymore past 1/4 throttle. how doesn't it. does a little leprocon (i know its spelt wrong:) run inside the pilot circuit and build a dam inside to stop the fuel flow :biggrin: fuel is being drawn from the pilot jet at all times. i would think that it flows more fuel, the more you give it throttle. think of the small hole in the jet as a small straw. you can suck your captin 'n coke up through those small straws more easily than those larger 1/4" diameter ones at mc donalds. now, that's why at idle to 1/4" throttle, the small amount of airflow that comes through the carbs, is all that is needed to successfully draw the fuel out through the jets and why changing the pilot jet has the most effect on the idle to 1/4 throttle range. also, cause its on the engine side of the throttle slide. fuel can't quite suck the fuel up through the main jet and nozzle yet, when approx at 1/4" throttle. as the throttle is opened more, there is more airflow coming through, and now the fuel is going to be able to get sucked up through the nozzles and main. yeah, the pilot jet's hole is very small compared to the main jet, so the pilot jet has little to no effect on plug color and fuel demands at wot. the pilot is still flowing, but you would have to change out mains to get the proper fuel amount and plug color at wot. i always tuned my mains and then pilots. i've never really needed to mess with the needles on anything.

Edited July 24, 2008 by mopar1rules