S-7 nozzle creating lean condition?

parkerCR · May 4, 2003

A year ago when my '01 CR250 was close to stock I changed out the S-9 nozzle for the S-7 nozzle and it helped the low end jetting great. I also leaned the pilot to a 27.5 Now I have:
V-force
FMF Fatty Exhaust
Boyesen Power valve Cover
FMF Turbine Core 2 Silencer

FMF recommended one clip leaner on the stock slide, a 30 pilot, 400 main and 2 turns out on the AS.
These specs are in So Cal at 70 degrees with 0% humidity.

I am riding close to sea level, with a high percentage of humidity
and it is about 55-65 degrees. I am currently running:

410 Main
S-7 nozzle
30 pilot
1 3/4 turns out on the AS
Stock setting for needle clip position (3rd)

I am no expert at carb tuning but when I pulled out my plug to get a reading today, all day it was white, then after slow trails it was black. When I was able to hit more open areas and clean it out for a while in 3rd gear it would be white. Sometimes half-white, half-black.

this is really strange I am wondering if I need to go back to the stock S-9 nozzle and it will help get things back closer to a healthier range.

I know this question has been asked but I am curious to know any thoughts that might make things a little easier.

Thanks

motometal · May 4, 2003

sounds like you are on the right track. I don't have a lot of faith in plug readings.

You can tell a lot about how a bike is jetted by just twistin the throttle to different openings in nuetral. If it sounds like it's just revving to the moon then let off-it's probably lean at that throttle opening. If it revs up part way and then just blubbers, too rich. You get the idea.

parkerCR · May 4, 2003

Thanks motometal! I am getting some blue smoke out the silencer when I rev the motor, doesn't this indicate a rich condition?

motometal · May 4, 2003

not always. the amount of smoke can vary depending on several factors.

did you add the power valve cover by itself, or inconjunction with other mods? If you added it independently, were you happy with the performance?

parkerCR · May 4, 2003

Yes it was the first mod I made and had that only (everything else stock) it is sometimes difficult to notice the difference on some of these mods but for 50.00 you can't go wrong. What is your jetting on your '01? Congrats on the new '03!

motometal · May 6, 2003

32:1 Suzuki CCI with Amocco 92 or 92 cut with Sunoco 110 50/50

25 pilot
410 main
s-7
stock needle and slide
not sure on clip position, you can also use a small washer to go 1/2 notch-try an r/c hobby shop if you don't have a washer.

I think i'm at about 800-1000 ft., this bike really rips compared to others I have ridden, everything else stock including pipe etc.

MOLE111 · May 7, 2003

ok ok , what's up with the s-7 nozzle lately ? a year ago it was the hot ticket and now i'm starting to hear results like this and wonder if i should put the s9 back in . i just rejeted my 01 cr250 over the winter and havent ridden it yet , should i now be concerned that it will be too lean with the s-7 in there ? anyone having good success using the s-7 .
i currently have the following set up : 40:1 , sea level , temps mid 70's
pilot - 30
needle - stock 2nd position
nozzle - s7
slide - stock
main - 420
last summer i ran the 30 pilot , 400 main , needle 2nd clip with the stock s9 nozzle and slide and found the bike to load up easily down low and in trailing throttle situations which caused a noticeable loss of response when re-applying the throttle , and there was noticable spooge at the end of the day . i was hoping the s7 would cure this although i don't want to stick a piston . should i be concerned ? i ride mainly offroad and play on an mx track on the rare occasion .

Faded · May 7, 2003

Originally posted by motometal
32:1 Suzuki

motometal, that's rough...I hope your not going to put that stuff in your new bike. ;)
j/k

motometal · May 7, 2003

Mole, you may also want to try a pilot jet smaller than that #30, even at sea level that may be on the rich side. Lean the pilot and/or turn out the air screw until it definitely hesitates off idle, and work it back in until throttle response is good. Remember if you are more than about 2.5 turns out that means you need a leaner pilot jet.

If you run at least a 50/50 mix of some decent race fuel, there will be a greater margin for error if you do end up a bit lean.

Faded, please tell me you are kidding and you already know about the benefits of running the almighty Suzuki CCI... :aj:

bedell99 · May 8, 2003

Hello fellow CR owners,

What I have noticed with most CR owners is they are jetting there bikes to LEAN. Especially down low. I read what most people are running and I am surprised considering I'm running richer jetting spec's then them (Leaner than stock) and my bike is running very good. I also race between 5000-6000ft. My opinion is that the S-7 nozzle is a bit to lean for your bike. I think the S-8 is a better option for most of us CR owners. I don't ride trails.nor do i rarely freeride. I ride and race on tracks so my throttle is never really in lower settings. Parker i think that your jetting is close. When your run the engine harder the deposits off the plug will burn off. Leaving a white looking plug. This has more to do with the heat range of the plug. Get the good ole magnifying glass out and look at the base of the plug this gives you a reading on your main jet.

Erik

Faded · May 8, 2003

Be sure to install a new plug before trying to get a (main jet) reading.

Click here.

motometal · May 8, 2003

wow...major error in my post...meant to say "#30 pilot" not "#30 main".

anyway, on the 2001 CRs I have worked with a 25 or 27.5 pilot was just right (at our elevation). Anything bigger and the bike loads up at low throttle openings. If it makes any difference, I prefer to adjust the idle speed so the bike will at least try to idle a bit. If the pilot creates a lean condition just above idle, this should be corrected with a smaller (straight section) diameter needle or possibly a larger needle jet.

bedell99 · May 8, 2003

I have absolutely NO idle on my bike. If it idles for more than 3 seconds, i turn the idle down. Throttle response is important to me. The best way i test my air screw is with the snap of throttle test. Let the bike almost die when it is in neutral and then snap the throttle real quick wide open. I there is a bog adjust your air screw till there isn't any.
Erik

parkerCR · May 8, 2003

This forum is amazing! I have learned more on this site than anywhere else.
Thanks everyone!

parkerCR · May 8, 2003

Where can you find the S-8 nozzle for the '01 CR250? I know the S-7 was a yamaha 125 part but am not sure about the S-8.

Faded · May 8, 2003

3TC-14141-S8-00 Yamaha Needle Jet...

Or you can just say you need an S-8 needle jet (or nozzle) for a Mikuni TMX 38. Pilot/Main/Needle Jets are available at carb parts stores (dealers/mod/aftermarket suppliers, etc.) but the Jet Needles are proprietary and a Honda dealer item only.

motometal · May 8, 2003

I have never related to the idea of having an mx bike set so it dies right away when you close the throttle. Some say that this causes it to load up, mine and my friends' bikes are set to idle at least for a little while and don't load up, at least not when the bike is jetted correctly.

S-7 nozzle creating lean condition?

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