Maintenance & Technical > KX500 Original
Jetting!!! Again and again and again!
gowen:
--- Quote from: kawdude ---
--- Quote from: KXcam22 --- An easy method I use to set mine is to (with the carb on the bench) put a piece of spare fuel line on and blow (used fuel line tastes bad) into it while tipping the carb back with the float pivot pointed up. When the air flow stops, that is your float level.
--- End quote ---
JFC! That's a great idea! So simple... :idea:
--- End quote ---
I've set the d**n float about 10 times, but I will check it to make sure again. :-)
Kawdude, I'll let you know how these needles work. If these guys are correct, it sounds like your problem too. Being the idle and 1/4 throttle is rich but the above range is lean or off range. I'm going to head out and run my KX for a few tests soon when these jets arrive.
Oh BTW, I was wrong about the pinging or knocking, it would be a LEAN condition. So, you are saying that you are getting more idles with a 2nd notch needle but are spark knocking in the mid range (lean), but are getting NO idle at the 3rd notch but getting a good mid range. This is what I'd try first............. Keep the 3rd range, don't fry that motor. Try to move down on the pilot and keep the needle at the 3rd notch. That way you are keeping the mid range at a richer range and going lean on the 0-1/8 range. If you need pilots, I can drop my 50 and 52 in the mail. I have no need for them as I'm way down on these.
gowen:
--- Quote from: KXcam22 ---Just for info what letter needles did you get? Cam.
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Just got the jets in. 8) I'm hoping this will be the last time I have problems with the jets.. We'll see. Anyway, this is what I've got:
CGH needle
CGK needle
CGL needle
40 pilot
38 pilot
and a 158 main.
I was also told that my needle crossed to a CGG, so I'm going to give the CGH a shot, still lean I'll give the CGK and so forth.
Thanks for the replys and help, I'll give a FULL report as soon as I give it a shot, which may be tomarrow, but more than likely Sunday.
KXcam22:
Gabe,
Always happy to help. That was fast from Sudco. Now that you have some jets you should be able to lick this thing. This will be long but here goes with some suggestions. Before you play with the needles you might want to try the pilots (I'd gamble and try the 38 first) first to get a good ballpark idle and smooth low end response, and then dial in the main so the plug is a dark brown (I'm not big on going too lean on the main). The reason is that the zone where the pilot and main operate overlaps the needles operating zone at each end and will effect it a bit. If you can get that pilot nailed down then you will be able to tell better how the low end transition to the new needle (straight section) feels, smooth or ratty(rich - splutters as it picks up) or doggy(lean- delay before it picks up) (nice scientific descriptions eh!). Setting the main next will help when you start playing with the needle height, and testing the 1/2 to full throttle response. For ex. I recently leaned my main to a 155 and it made the most difference at 3/4 thottle (more wheelie) where you would think the needle affects most. My bike is very electric down low, smooth from off-idle to at least 1/2 throttle, probably what yours will end up like - just with more power!! Don't forget to take a handful of disposable cheap BR8ES or B8ES for taking plug readings. Often you can clean them enough (carb cleaner & toothbrush) to use for a 2nd run. Also, when starting to work with the needles, (assuming the pilot is now set pretty good) it might be fastest to first try each different needle (clip in the center) one after another (no raising/lowering yet) to see which gives the best 1/4 to 1/2 throttle response. One should be better than the others then you can try fine tuning (raising/lowering) that one. Oh yeah! Check your plug often even if you're not reading it too much, just in case you get a white one when you're least expecting it. Don't forget too that you can take 1/4 throttle or 1/2 throttle plug runs - just takes longer but sometimes solves a mystery. There is a neat mini-graph on those sudco keihin pages that shows the throttle range where each jet operates and overlaps. Might be handly to take along. I'll look for your report when you're done. Have fun and good luck. Cam.
gowen:
Wow! A very long Sunday.. I spent from 11am to 7pm working and playing with the carburetor. A sucessful day!!!!
I started off by going down on the main jet, which helped bring in a cleaner WOT, much cleaner and much more powerful. Anyway, on to the problems:
I then went down to a 40 on the pilot, which brought the revs up alot, which I couldn't have been more happy, I turned the air screw to 1 turn out when I changed it, and turning it out more caused more idle, which I ended up bringing it out to 2 1/4 turns. Then I decided to drop to a 38 pilot. Yes, that changed alot, more idle!!! Which I still turned 2 turns out. Well, running it did good, it was still a little rich in the idle 1/8th and 1/4th range. So, I jumped to the CGH needle. Wow! I couldn't believe the diffrence on the low range. I still kept to the 2 turns out on the air screw, as it was still finding more rpms with the air screw leaning out. So, I decided to jump from the CGH to the CGK. Yes, that was the ticket guys. I have a smoooooooooooth idle and I have turned out my idle screw out about 10 turns. Which I used to have it all the way in. :-) I've never heard a smooth idle on this bike before. Very clean idle.
Here's the deal:
I put the needle in the center and it is doing GREAT! But, when I rev from an idle, it surges two or three times before going back to idling. Like what you decribed kawdude. It does NOT do it when I let off the throttle at a WOT run. Only when reving it.
So, I was assuming the needle was lean. So, I lifted the needle to the 4th notch. Surges nearly left, very faint. But, power was pretty clumsy and would not get a full clean rev through the RPM range. Anyway, so I dropped the needle back to the 3rd notch to give it a run to see the power diffrence. Wow , it had about twice the power from the 1/2 to 3/4 range. But the surges were back. Anyway, I decided to forget the surges and drop it to the 2nd notch just for the heck of it and gave it much more power and responce in the 1/2 to 3/4 range. But, the surges are still there, but not anymore than the 3rd notch. So, anyway just for kicks I decided to try a leaner needle CGL and it was too lean, it reved alot and had little power and ran bad and surged like crazy. So, I put the CGK back in and it is doing great. On the 2nd notch and it is running perfect in the RPM range, but when you give it a rev from idle, it surges a little, like a pop or a RPM jump slightly. But, to cure it, I have to lose power in the mid range.
Cam and Kawdude, I'm a little lost here, I'm running great and did a few plug tests, all coming nice brown, but only rode for a few hours. Not lean I don't think, the surges are there, Kawdude was having the same issue.
The air screw does not help the surges, only the needle, but richening the clip kills the power. Leaning the clip gives more power, but causes slihgt surging.
Ask away at the questions, I'm lost.
KXcam22:
Gabe,
Good work with the jetting. It sounds like you are getting very close. The surges may seem a bit weird, but now that I think about it my bike may do that a bit. When I rev it in neutral, the revs increase, decrease to idle then I get a little pop where it revs up once for a split second. I'm not absoulutley sure about that but it's got me thinking, I'll test that out next weekend. Is that what yours does? Here's something that might help. At 1/2 to full throttle the needle and main overlap a bit, more so as you approach 3/4 to full throttle. For a trial I would suggest leaning the main one more size, then you should be able to raise the CGK needle to richen the 1/2 to 3/4 area, but with the smaller main it would have more effect at 1/2 than at 3/4 so you wouldn't lose power at 3/4. Let me know how it works. Cam.
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