charts

antsx · #1 10-20-2012, 07:44 PM

hi what do people use to compare jets and needles is there any scientific formula to work them out or is it all trial and error.
I have only just got my gas gas ec250 07 but i dont know much on jetting and want to get it running crisp. It had air screw 1.5, idle all the way in a 38 pilot, n1ef clip 3 and a 162 main wen i got it and was good down low but no top, i happend to have a couple of jet from years ago and at the moment i have air screw 2 turns, 40 pilot, n1ef needle on clip4, 170 main im in the uk temp 5-15 deg c, sea level to 1000ft. Am i going about this right? any advice on a better needle or is the n1ef ok for me, thanks

Jakobi · #2 10-20-2012, 08:25 PM

The user manual has a table in it. You can download at www.gasgasmotos.es

I'm not familiar with the older carb AS series 1, but from what I have read it likes to be jetted much richer than the newer ones. As such disregard a lot of the info re N3EW/NEDW etc that you may read. You can however substitute and try an NEDF/NEDG etc if you want to do some testing of different needles.

The things that stand out reading your current setup is 1) its cold and 2) thats a lean main jet. If you were happy with the response of 38 N1EF#3 but it fell flat up top I'd suggest trying a 175/178 main jet. That would be typical for those conditions/temps/clip position.

andoman · #3 10-20-2012, 09:29 PM

antsx,

Welcome!
Did I read correctly that your idle screw is all the way in?
In that condition you are bypassing your idle circuit: both the air screw and the pilot jet. You are holding up the slide with the idle screw and you are idling on the the needle and main.
While its idling, back out the idle screw. As it wants to die you can begin to adjust the airscrew to keep it alive.
Obviously, bringing the idle circuit into play will be required in order to get the jetting completely sorted.

Jakobi · #4 10-21-2012, 12:52 AM

Quote:

Originally Posted by andoman

antsx,

Welcome!
Did I read correctly that your idle screw is all the way in?
In that condition you are bypassing your idle circuit: both the air screw and the pilot jet. You are holding up the slide with the idle screw and you are idling on the the needle and main.
While its idling, back out the idle screw. As it wants to die you can begin to adjust the airscrew to keep it alive.
Obviously, bringing the idle circuit into play will be required in order to get the jetting completely sorted.

100% correcto.

antsx · #5 10-21-2012, 04:00 PM

thanks for replying guys i went out today and tried a 182 main seemed ok but a bit rich at half throttle so i moved the needle from clip 4 to clip 3 didnt adjust air srew so still at 1.5 and the idle srew wasnt all the way in but the coil is binding up prob got another 3 full turns to close it completely, what i did notice was the idle speed had raised a bit when i moved the clip back up to 3, so tomorrow i will play with the mixture screw and see if i can get the idle to go up so i can back out the idle screw some more and adjust the pilot richer, if more than 1 turn in, leaner if more than 3 out, is all that the right way to go about it or should i be doing something different? would raising the needle again make the idle go up further?? thanks again ant

Jakobi · #6 10-21-2012, 08:53 PM

Ant,

By you stating that a clip position altered the idle you have confirmed that the idle screw is turned in too far and the bike is actually idling on the needle taper and not the straight section. What this does is essentially cut the idle circuit out which means you'll find the air screw has very little effect on the idle, as will changing pilots.

The reason for this is that the needle diameter and pilot combination is too rich to sustain an idle, so by opening the slide up (turning the idle screw in) you are allowing more air into the mix. What you need to do is either step down a pilot jet at a time, and as the idle races more, back the idle screw out, or my preference is to drop a couple sizes on the needle diameter and then do as suggested again. Back the idle screw out.

antsx · #7 10-22-2012, 12:53 PM

thanks for the advice jakobi you seem to be a jetting guru around here , i put a 38 pilot in smallest i had, moved the clip to 2 and managed to get the idle screw 2.5 full more turns out and it was 2 turns out on the air screw. I havnt done a test ride as its been hammering down with rain so i dont know how it rides.
How far should the idle screw be out? when i took the carb off to change the pilot i had a look at the slide it was prob 2-2.5mm[guess] gap and when i wound out the idle screw it took 4 full turns to bottom the slide with no gap, does the slide need to be bottomed with no gap? This might be a stupid question but what is the idle srew for? if it should be in a certain position and you set the idle by getting the right pilot and needle? the more i learn about jetting the more confusing it is haha! its all fun tho