Jetting!!! Again and again and again!

[dennis]

Ok, seems theres a few of us that have the same problem. My kx is jetted very lean and it stilll runs rich. the main is a 160, the pilot is a 45 and the needle is a 89. I'm in arizona and the altitude is about 1300 feet. I bought the bike new in 2003 and it ran really rich then. as far as power goes its great, it walks right past my buddies crf450 and my other buds cr500. power isn't a problem. You guys think maybe Keihn made the needle seat too large or something? I replaced the ignition coil, rewound the stator. I haven't changed the cdi but since the bike starts well and runs strong I don't see the point. I get about 50 miles on a plug, even the hotter 7.

[KXcam22]

Dennis,
  Check your needle, the N82M is stock.  It might be a typo but I don't think the 89 is correct (unless they changed it in later years).  Also the 45 pilot sound too lean (possibly to compensate for a rich needle?).  Does your bike idle?  Asside from that I feel that the stock KX needle has a too small diameter on the straight part.  We compensate by running it all the way down (like mine) but that doesn't help the 1/4 throttle area as much as it could.  I can't offer a tested solution yet. I plan to test a bunch of leaner needles this spring but am waiting (and waiting) for an LCL/ACL tear to heal (or surgery - should know next week) so can't ride yet to test (heck I can't even kick the bike over).  As a start, setting your jetting to the chart is very close. Then tune from there. 50 miles on a plug isn't so good. I get a whole season on an BP8ES.  If your jettting is close the 7 should show a white too-lean burn and the 8 might show a dark-brown slightly too-rich burn.  Also when the surges show up you are getting close.  What oil & ratio do you run?  It affects jetting a bit.  Hope this helps. Cam.

[dennis]

Hello group.
  Seems jetting is an ongoing problem with the big kaw.  I haven't sorted mine out yet. I'm running a stock bike, fmf pipe, 160 main, 55 pilot, 2nd notch on the needle which is an 82m, the orig.  I run rich.  the altitude here in casa grande is about 1200 feet. Its getting warm outside so I guess the rich thing will just get worse as the air thins.
  I'm thinking of going to a K&N filter, has anyone tried one? None are listed in the Dennis Kirk cat or the Rocky Mountain.  Does anyone think the V-Force reed would help any, or a reed spacer?
  Could all this be a problem with Keihn carborators. maybe their quality control isn't very good.
  Oh by the way, this bike has run rich since I got it brand new in 03. Power wise it spanks my buddies crf450 and my other buddies cr500, power isn't and issue.

Dennis in Arizona

[hughes]

I know I get throwing this out there but have checked the float height? A three year old bike could still need alittle adjusting.

[gowen]

Dennis, the big KX comes out of the box a disaster. Hughes is right, check the float height. But, the jetting is going to need some attention. What is your altitude? Check the jetting chart, it will give you a starting point. It wasn't close for me, but I am sea level and had a few modifications.

[Paul]

Once again, the elusive jetting chart

*** Starting point, not the be all to end all ***

And if you need a refresher on reading plugs

[zert]

okay,here is my problem bike.Its a '99 kx5 with a fmf fatty.The bike runs very rich in the lower rpm's,smokes like helldont idle but runs great in the higher revs.When i bought the k5(second hand),its had no power when i pulled the trottle.So i checked the main jet and it was a 182!I changed to a stock one(168) and its was much better.Now i have a 165 and its perfect in high rpm's.The pilot jet was a 55,now a 50 and he still wont idle.As soon a let go of the trottle,the engine dies.The needle is n82l.When a ride on the track or on public roads,the fuel consumption is the same .Maybe the previous owner "tuned"the cylinder and screwed it up?The main problem is:how can i make my bike leaner at low trottle?What happens when your reeds are worn?I run almost every week with some other supermotards but i'am the only 2 stroker and now i starting to understand why
So,come on up with the theories and answers.
Regards,
Wim

[gowen]

If you are certian about the crank seals, I will tell you that I'm at a 38 pilot. You might have some engine work (like a big bore, porting?). I understand your frustration, I was getting totally frustrated with my KX and getting it right. But, if I were you and Cam might correct me, but in your case I'd try to find an idle. Your pilot jet is your main source for idling.

But before you go on, as Cam said check your slide #. It should have a 6 or 7 stamped on the top. Either way, I found my idle by turning the air screw OUT until it idled, if it wouldn't idle, I'd keep leaning up my pilot until it idled. Once it idled, then I'd fine tune it between the slide and main jet.

Again, I'm down to a 38 Pilot and I get tan crisp plugs and couldn't be more happy with my jetting and it made 100% more power.

Read this article for a better understand of jetting : http://justkdx.dirtrider.net/carbtuning.html

Hopefully we can get you streight. It will be the best modification/tuning you can do to your bike.

[KXcam22]

Zert,
  Lets start at the begining. First, the N82L needle is 1 step RICHER than stock. Whoever owned your bike before has deliberately jetted it extra rich.  I can't understand why (yet) unless the previous rider liked to chop the throttle in corners and didn't like the surges the KX will make when jetted nice.  Solution is to not close the throttle in the corners.  The jetting procedure I like to use is to ballpark the main jet (which you have done), get the idle right (as Gowen says) then work the needle, then finish by fine tuning the main.  Sometimes you may have to go back and retune certain areas. Here is what I would suggest:

1. Verify your float level and slide number.
2. Ballpark your main jet (you have done this but expect to go larger)
3. Change the needle back to the stock N82M clip at 2nd to top position.  Given that you are at sea level I doubt you will need one leaner than that, but it is a good first step.
4. Try to get a good idle with only the needle change and your 50 pilot. If the idle still is not right try the next leaner pilot (45?). Some mods make the engine more efficient requiring leaner jetting.
5. With the stock needle and a working idle do a full throttle plug run. For supermoto I am worried that the 165 may be too lean so need to verify it is ok.

Answer back with your results and we will continue. Hope this helps. Cam.

[zert]

thanks for the advice,i let you know how it went.(slide is number 7)
wim

[gowen]

Zert, call Sudco for needles. They are $6 a piece over $25-$30 a piece. (323)728-5407 I say to call them because they will help you with the numbers and getting the correct needle. That way you could pick up a few. But if you are richer than stock, I'd just go down one Needle and go with that. But, if it is still too rich you'd only be out $6. Just an idea. Let us know how it does.

[zert]

@gowen,i'am from belgium so i guess sudco is a little to far for me but thanks for the tip.The two holes in the airbox,do they have a meaning?Should they be open,close?My previous one('90)didn't have these holes.
wim

[Danger4u2]

Lets more air into the filter, in wet conditions keep them shut.

[Timbowe]

Makes quite a bit of difference to the top end with them both open.

[KXcam22]

Tim,
  That's a good call.  For supermoto Zert should probably test all his jetting with both of them open for max airflow & power (I'm too chicken to open mine).  A K&N airfilter might also improve the flow a bit more.  I doubt if there is much dust to worry about.  Zert, sudco is definately the place for parts but given your location, I think the Local Kaw dealer might be easier.  Based on your elevation I think you will only end up buying the stock needle, possibly a second leaner one depending on how things work out.  Slide #7 is stock so that's a good thing. Let use know how the testing goes. Cam.