Jetting!!! Again and again and again!

[KXcam22]

Rob,
  Glad the jetting info here was helpfull.  I think you might be a touch lean on your 52 pilot, given your altitude and temp.  There is a jetting chart on this site that is really close.  I arrived at my jetting years ago with lots of testing and it matches the chart exactly (who'd have guessed).  As for the larger carb, I think one of the reasons they don't go much larger is that the venturi doesn't work as well at low airflow, ie going slow, one of the reasons that road-bikes with 40mm and larger carbs have mostly gone to fuel injection.  That is why the even the 39mm we have benefits from the "power now" wing a bit (I'm told - haven't tried it) to remove some of the low-air flow turbulence.  I think the big KX would really benefit from a carb with a throttle position sensor and electronic power valve like some of the new ones have.  Cam.

[gowen]

Cam, I was having too much fun to try the diffrent needles, but I just got back from working on the KX and am having to get some welding done cause the frame busted another pipe mount, also my radiator cracked and is leaking. Got radiators and have the frame torn down and ready to be fixed. I also have to order a new rear tire (installed new in July and is worn down) and chain and sprokets (busting teeth, but have all lasted a year). But, all will be in a few days and I will be out testing further this week.

I'm pretty sure you are right about the needles, as it is lean in the 1/4 range ONLY. I have the frame apart now, but will have it fixed today.

Speaking of a throttle position sensor, would that be possible ina KX? I've seen them in my CR and YZ, but never thought about the KX.

[KXcam22]

Gabe,
  Glad to hear you were having fun. Too much testing can get tedious!  Besides, sometimes if you have a mild lean condition it is hard to tell exactly and your impression or gut feeling of the engine response over a few rides is the best clue.  Unfortunately that TPS needs the newer digital ignitions to work.  It would be cool since apparently, for optimum power, a 2-stroke likes being on the lean side up to full throttle then being a bit over-rich when at full throttle, stuff you cant do with regular carb/jetting.  The new bikes have this so they can pop an electronic power valve(confusing - its an extra jet in the carb) open at full throttle to richen it up.  Look at a new CR250 they have both (I think). Be nice to have but I think we are stuck.  Hey we still have waay more HP than a CR250 any way you look at it. Cam.

[RexRob]

Your right about the power, and we will continue. 4 Smokes will be the thing, 2 strokes you can tell your kids about as california will lead the pack in getting rid of all of them! They already did in their state, you can't even buy a weedwhacker that isn't electric or 4 stroke. I think 2006 (as far as I know) will bring radical changes to our world. Honda might be ahead of the pack in getting ready, but kawi is planning the 450 release. I almost bought a, dare I say, yAmAhA wr450 instead of the beast. I just love the 2 stroke wild *ss big bore power, torque is the best. I doubt the 450 can be as good as a hooligan bike as the "Beast"
By the way I am RexRob becuase I also have a zrx1200r, my favorite street bike I have ever owned, the powerband is incredible. I have alwaysed loved big bikes since discovering them. I had zx11's hayabusa etc, the rex is sweet.
Well my plan for the 500 now is to go back to factory 168 main, my problems must have been fouled plugs from break in, and a very rich low speed circuit. I spend most of my time at low speed at WOT, but during break in i was restrained, rich was good. I should have changed the plug at my dad's again but didn't. It would break up from 3rd gear on, 4th and 5th was BaD. I thought most of it was jetting, it was a fouled plug. Last run it really ran, but tan plug. Again, no hesitation or bog, it ripped. You should see my driveway, looks like a drag strip! Black stripes all the way down. I am going back to the 168, maybe 170, it's getting cooler here. I will leave the needle where it is, pilot will be a last resort for now as It idles fantastic. Midrange 1/2 throttle was great, as all ranges were but I do want to save the engine, will check the plug frequently. I just want to thank Gowen and Cam and Kawadude for all their input, it has been invaluable. This is a great thread!
Reguards,
Rob

[RexRob]

I forgot to add that one day I will try the 41 pwk, If anything gulps air it is the 5hundred, there is no 4 stroke that can gulp more that I know of, 4 strokes only do it half as much.
I will post all related info as it comes, but I do know it will be next year. Now if I could get her to wheelie at 1/2 throttle in 5th, I'd be in nervana!
Fuel injection would be great, especially direct injection, that is where true power lies, but like I said 2 stroke development is going to be a thing of the past. Ther has been a lot of hype about 4 smoke power, a leading Mfr. stated Hp figures that even formula1 said was impossible. 2 stroke has not reached it's peak yet! How long have they been around? Oh well, take your 5hunny and show 'em what a Real motor can do!
Reguards,
Rob

[KXcam22]

Rexrob,
  Not really a jetting topic but for a plug try the BPR8ES.  THe "P" protruded nose helps it run cleaner, and they are cheap at Lordco or other.  Mine last a season and aid in starting (1 kick hot or cold). THe ZXR1200 is fast. Why no 1/2 throttle wheelie in 5th? Should do it. Cam.

[gowen]

Cam, I've had alot of success using the EIX plug. During all my jetting woes, I believe I've only used two and that is only cause I wanted to change it, it did not foul.

[RexRob]

I have been running the br8eix like Gowen, well ever since the br8eg was black and wet, and the eix was black and wet, now I need to change the jetting. I have been doing a lot of thinking and I may go to the 55 pilot. Team green says for 2002 kx500 with my alt. and temps (I won't ride below 65) 2nd clip (which I have) 170 main, and 55 pilot. Sound good? Maybe burning more fuel will give me more power, if I can do it cleanly. Hate to pull the carb off again, but I am a perfectionist by nature. I don't have a 170 right now either. I have the 55. Need to grind the screwdriver down that I used for the pilot swap so it doesn't take any metal out of the passage, had me worried... The weird thing is that the reccomended plug was a 9 series NGK. I am not going to 9. Thanks cam for the sugguestion on the extended nose one.
The bike will only wheelie 5th full throttle little tug, 5th is FAST, stock gearing. 4th will do it on a roll on power wheelie, 3 rd is radical, 2nd is death defying, 1st, well you better be real good or put a wheel on your helmet. This is on pavement, I can ride on the road I live on, everyone does and I have never seen a cop up here, ever. We don't have a 1/4 mile or even a 1/8 mile straight, maybe a 16/th. Stopping has always been my problem, kinda used to the zrx brakes.
Wind up overshooting and looking for a way out, which I have done quite well. My 91 was the same wheelie wise, and I had that ported with rad valve and psi pipe. Where I used to live when I had the '91 there was a railroad grade about 1/2 mile away. I decided to ride the bike up the streets to get there. On the road that leads right into the grade there were 2 guys working on locking their hubs in their pickup. I went by them in 5th, yanked the bars and nailed it, the bike came staright up, My feet came off the pegs like superman, somehow I got her down and didn't loop it, I still do not know how I did that!!!!! I will try to get the changes done this weekend and let you know how I made out. Good luck Gowen and thanks Cam!
Rob :blowup:

[gowen]

I've been very happy with the results so far with the jetting. I've got ALOT of work to do with the KX now, but have the parts ordered, the mounts welded and should be ready this weekend. Anyway, I will get around to it. I just had to refill my C12, so I will start to run pure C12 instead of a 50/50 mix and see how this works.

[gowen]

No updates yet, until today.. I took the KX out today to the local sand pit today to do some drag racing, trails, ect. mainly in the sand. It has not rained in a week or so, so the ground was very dusty and the air was over 80 degrees. Hot for a Halloween day I have to say, anyway no humidity or at least much. Well, I took the KX off and gave it a run and it felt very sensitive in the mid range, very lean. But, I had not changed anything from the last run. But, weather and air I guess make a hell of a diffrence. Anyway, starting with the air screw, it made no diffrence, I could get the idle up, but the low-er range was VERY sensitive. So, I ended up lifting the needle one more (5th clip). Man that worked wonders. Anyway, I ran the tank out of gas and decided to run my mix of pure C12 and MC1 (50:1). Yes, the KX (or mine) is made to run of streight race fuel. Very good responce. Very fast running machine once tuned well. The surges are there, but not as much. Idle is the same and it is great!

Anyway, for the question:

Where do you think I should go when my needle is sitting on the 5th notch? The main and the pilot I believe are great. After the 5th notch, it was awesome. Should I put it back on the 4th when the weather cools down again?

[KXcam22]

Gabe,
  Been reading throught the past posts to remember what settings you are at: 155 main, 38 pilot.  Is your last ride results with the richer CGJ needle? Let me know. Cam.

[gowen]

Cam, I believe so, but don't remember. Sorry, but I will take the carb apart. My YZ250's linkage locked up and I have to rebuild it and decided to check the linkage on my KX and saw that is was cracked and majorly worn out. So, I have a spare bike and took it off and am waiting on swingarm, linkage, and shock bearings. Also, had my throttle cable go out and my air filter... So, waiting on a few replacement parts which should be in tomarrow or so. Once up, I will write another report and do some needle swapping. Cam, I thought I was at a 148?? But, I forgot.. I'm sorry, I've been soo swamped with work I've lost it. Anyway, thanks for your help... But where did Kawdude go to?

[gowen]

Opps, you are right, a 155, I think I'm on the CGJ needle. But I need to check. I think I will try Sudco for another needle.

[Glenn_KX500]

I thought I'd post some info for you guys.
I just bought a '99 KX500 2 days ago and have some printed info on jetting. My bike has a new top end, entirely new cylinder (not resleeved), Revloc auto clutch, ect.

The info I have says my plug gap is: 32/1000
Stock jetting 168/58
Jetting set at 165/55
My factory manual says stock is 175/62  
I imagine that would be way too rich, unless you compensated by using a high needle position. The stock needle position is 3, indicating that's probably too much jet from the factory, especially for high alt.

I do know quite a bit about tuning from jetting multiple bikes over the years, as you go up in elevation you need to lean out the mixture. I am in South Texas, RIGHT AT sea level. 165 seems good, although I will probably move the needle up one position (lower clip position) to richen it up just a bit.

I've been doing research for a few hours on surging on decel where the engine will keep kicking even if the throttle is totally cut. This is a little bit dangerous if the terrain is technical and you're not going in a straight line.
WOULD GOING TO A LARGER PILOT JET SOLVE THIS PROBLEM?
Surging on the low end is a sign of being too lean, would simply swapping out to a larger pilot solve this issue?
I haven't had my bike for more than a few days but when I cut the throttle I want it to stay cut.
The only other issue I have with my bike is poor idle.
The plug it calls for is a BR8EG
It comes pre-gapped at .024
A wide gap like .032 is out of spec according to the manual and will draw a lot more energy from the coil for it to fire.
So what I'll do is I'll get a BR8EG and gap it out to the maximum suggested in the manual, which is .7mm - converts into .0275"
I'm hoping that will allow for a lower, more stable idle.

http://www.ngksparkplugs.com/apps/motorcycles/make4.asp?id=4269&type=reg

As for the hiccup/surging/kicking when the throttle is cut, I have a hard time believing that is something these bikes "just do", I know with 4 strokes they come calibrated lean from the factory and popping on decel is very common, richening up the pilot will solve that. Will richening the pilot on this bike prevent it from surging on decel?
Would turning in the air screw a half turn improve this?

It's too late to go outside and experiment, or I definitely would.  

[gowen]

Hi Glenn, I have put about a month of research into getting the surges to leave. It is possible to remove the surging, first by running a fat pilot and by running a rich needle height. Those are your only options, I am not toying around with a Boyesen Rad Valve and a PVL ignition, I will find out how this effects the surging and what have you. I hope this helps, if you are surging, I would suggest bringing up the pilot until it quits or calms down, then start on the needle height. But you will sacrifice your idle. Idle will come and be strong when the jetting is perfect, but then you will have surges. The big CR does it slightly also. Anyway, hope this helps, ask away at the questions if you want specific answeres. KXCam should be around soon too, he is the expert in this area. Thanks