Maintenance & Technical > KX500 Original

Jetting!!! Again and again and again!

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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

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