Jetting!!! Again and again and again!

[KXcam22]

Kawadude,
  If your interested we could probably start looking at the jetting on your bike.  For a start it would be a big help if you could post your riding conditions, elevation, temp, humitiy etc, the jetting you started with, and the jetting you have now.  Also inlcude the bike year, and the engine modifications you have made, pipe porting reed etc.  Maybe a description of how the bike runs.  When Gowen gets his new needles, I think he will have his sorted out pretty quick.  It's very close.  I am not possitive that his settings will work for you as is, but what we have learned should be a huge help. Let me know. Cam.

[gowen]

Cam, I ordered a CGJ as they do not make a CGI. It will be here tomarrow and I will have an answere to you by Friday night, hopefully. I'm assuming this will do the trick.

I've decided I will never go according to paper again. Meaning, I will never jet my bike according to a FMF's spec page or the service manual.

This is FMF's chart for my KX500.

170 Main, 62 Pilot, 2nd clip, & 1.5 on the air screw @ 32:1 50/50 pump/race fuel, Sea Level - 1500, and at 70 degrees.

This is what my KX is at now.

155 Main, 38 Pilot, 3rd clip, & 1.5 to 2.0 on the air screw @ 50:1 50/50 pump/race fuel, Sea Level and somewhere in the 70-80 degree mark.

Anyway, lets get Kawdude's KX fixed up.

[gowen]

Cam, I came up with an idea, I will record my bike at 1 1/2 turns VS. 2 1/2 turns.
Note: 2 1/2 turns idles the best @ a 38 Pilot.

First Clip: 1 1/2 Turns. Just fired up let run for 10 minutes before clipping sounds:

All hits on the throttle are nothing more than 1/4th throttle, one 1/2 throttle hit, and then a small 1/8th hit later on in the clip.

It seems to only do it in the 1/4th range to the 1/2 range.

Second Clip: 2 1/2 turns on the air screw. Seems the same! It did not help it at all.

Let me know what you guys think.

http://www.matchmakerautoservices.com/kx500/oneandhalf.wav

http://www.matchmakerautoservices.com/kx500/twoandhalf.wav

You can click to listen or right click and click "Save Target As" and put it on your desktop and listen too.

EDIT: Cam, listening to the sound clips, I'm thinking it is out in the Clip position. According to Sudco's chart, the diameter controls mainly the idle to 1/4th. The clip is the 1/4th and up. and the diameter is the 1/2 and up. According to the sounds 1/4th and 1/2 are the main place for surging.

 Also, it ONLY surges on the return to idle, it DOES not surge while using the gas.

[kawdude]

The surges on mine are on the let off also.  Are you just cranking and letting the throttle retun to zero.  That sounds just like mine.  The second sounds lean to me.  Too lean...no idea!

[gowen]

Kawdude, yes, I'm just chopping the throttle. Hit and let off. Here's the frustration:

I worked on it this evening. Starting with the needle. I got my CGJ in. Installed it, and it was the same, same surging. Soo, I decided to go back one to CGH, still surged. Went back to the stock needle... Still surged. I then decided that it was not the diameter. So, I installed the CGK I was using before. I then dropped the clip one to the 4th notch.Still surged.. Same as the recordings. All the same. I have yet to try choking the carb to see if that clears the surges. The only way I've cleared them is by richening it to NO idle.

[KXcam22]

Gabe,
  That Sudco chart is pretty handy.  If you really analyse it you can get a good sence of what jets operate where and also where the action of 2 jets overlap. Did you get your needle yet? The sound clips are very cool. Invaluable for diagnosing the surges.  My bike has sounded the same. I'll try it tommorow morning (I forgot today) but your sound clips sound very familliar!!  At 2-1/2 turns for the best idle it normally would indicate going one more leaner on the pilot, but in this case I think it may be better (since it is very close) to stay with the 38 until the needle is closer.  I've never heard of a KX500 with a 38 pilot but it is stock for some CR500's so not unreasonable for the dispacement.  I bet that the Eric Gorr porting and all your mods are making the engine run more efficient, hence it doesn't need to be as rich in the mixture.  I'll tell you my idea on the surges.  If you have ever turned the gas off on your bike and let it idle, when it starts running out of fuel the jetting gets very lean and the idle takes off uncontrollably - and sounds just like the surges.  My hunch (humour me I may be waay off base) is that when the throttle is chopped the engine is still trying to pull fuel in (big vacuum) and the last mixture available before the slide actually closed (say 1/4 to 1/8 throttle decreasing) was supplied by the straight section of the needle.  You are right about the clip position if the fuel was supplied at the 1/4 and past.  A good test for that would be to raise your present needle maybe 2 clip positions and see (heck record!) the difference.  If you are going in the right direction the 2-position change should make a obvious improvement to the surges.  Will you get a chance to do some testing this weekend? You may have done this already, but it would be worth trying each clip position on that needle to see if any improvements show up (more low end dial-a-wheelie).  Let me know the results of your next tests. All the best. Cam

PS. those sound byte are a really good idea!

[KXcam22]

Gabe,
  Those are good test result (just not what we wanted).  Did you try riding it with the CGJ? What slide # is in your carb? So much for my theory.....d**n now I'm really curious.  It's dark here or I would go fire up my bike right now.  For sure I'll try it early in the morning.  Cam.

[gowen]

Cam, I did get the needle. I have yet to try a dial-a-wheelie today, but will tomarrow or Sunday. But, the---in the garage---test did show that the surges are still there and have yet to change. I moved back to the CGK and dropped the clip (richened) one notch and it did not change it. But, it did sound better, cleaner. Let me know what you think. The diameter did not seem to fix it, as I kept moving back in the needle CGK,CGH,CGG (or stock), and it still had the same issue. I've fixed the surging by richening the pilot or air screw to the point of rough running and no idleing.

Thanks for the help, I'm going to work on the dial-a-wheelie and get back with serious results, not the garage type. It's getting too dark now.

[gowen]

Gabe,
  Those are good test result (just not what we wanted).  Did you try riding it with the CGJ? What slide # is in your carb? So much for my theory.....d**n now I'm really curious.  It's dark here or I would go fire up my bike right now.  For sure I'll try it early in the morning.  Cam.

I appreciate your help! I'm not worried about the needles, as I could always use extras for other bikes or for another rejet or something useful. I sure have not tried to ride it yet, as it is also dark here too. But, will try it tomarrow after work for sure. I will start with the CGK on the 4th clip, then jump to the CGJ at the 3rd, then hit the 4th and get back with you about the exact deal with it.  

Also, I'm using a #7 slide.

Thanks again and let me know about your idle, I'm on my toes about it.

[KXcam22]

Gabe,
  I fired it up this morning and guess what!!  My bike surges more than yours does, way more.  No less than 6 surges per rev-up and once I counted 12 when it was still a bit cold!!!!!  I think it has always done this, perhaps ever since I jetted it way back when - can't remember.  This could be a trait of the bike when it's jetted close (maybe).  Anyway I guess I never worried about it since it runs perfect all the time.  That surging is probably the same as I get when coasting downhill at speed.  Again I guess I never worried about it since I rarely coast downhill with the throttle closed. This actually got better when I went from 58 to a 55 pilot a few months ago.  Sorry I should have tried my bike sooner and saved you some testing time.  The sound bytes are what got me thinking.  It might be best to ignore the surges for now and work on getting some more power in the low end throttle range.  I still think that new (richer) needle will be the ticket but only your testing will tell for sure. I'm taking the kids out riding tomorrow so I'll be wearing out 1st gear again. Cam.

[gowen]

:worship:  :worship: Cam!

Thanks!! That is the ticket I was needing. Knowing your bike is doing the same deal has let a load off my mind. I am goin out riding tomarrow and will give you a report of the needle swaps and everything else that occures. Will work on the dial a wheelie and see if bringing the CGK to a CGJ and so forth! Thanks again! Wow..   :drunk:

Now Kawdude can get his fixed up too.

Thanks again Cam!

Gabe,
  Those are good test result (just not what we wanted).  Did you try riding it with the CGJ? What slide # is in your carb? So much for my theory.....d**n now I'm really curious.  It's dark here or I would go fire up my bike right now.  For sure I'll try it early in the morning.  Cam.

[RexRob]

Hi Guys,
I have been viewing this project for a while, actually since getting my 2004 in sept. I bought it since they were (for stupid reasons) going to be discontinued. I had a 91 and loved it, missed the hooligan power rush! Bike was hard to get, called over 20 dealers and wound up getting it in MD, wish I could have got it closer...
Well my bike was running rich (I broke it in as recomended) all I got was black plugs even after it was broke in, though I think some of it was the plug. I haven't been riding it since the first week I got it and went to my dad's (5 hrs. away but 110 acres).
Today was the day I was going to do something about it, I yanked off the carb and checked the float with a caliper, it was fine. I had jets I ordered from pro flo (took 2 weeks to get them because of hurricaned in Fl.) I probably made too many changes at once however. My main problem was (besides the black plugs) was it would not idle for crap, maybe 3 sec's with the air at 2 1/2 and the idle screw in all the way. I dropped the pilot from a 58 to a 52, main from a 168 to a 165, and the clip up a notch (2nd from top). I also cut the gas, I was using camII 110 octane straight with 40:1 H1R. I used 1 gallon of that mix and a gallon of super unleaded mis 93 octane.
I started it up and took the choke off right away, it idled by itself, but fast. Turned the slide screw out 2 turns at least and it still idled like a dream! Took off after warming it up some and then rode easy a little bit to get it up to temp then cleared her out. What I can say is that it runs incredible, wheelie any gear and moving dirt like a grader. No hesitation, idle is still a little too fast, and guess what, since day one I have the same thing you all have, the dreaded surging to idle, must be the nature of the beast. Sure glad it has good brakes! Nailing it down the street on the back tire in 4th then chopping the throttle it does not slow down quickly by itself, it will do it in any gear and neutral. Hit the gas, and just like gowens audio, the same thing.
After letting it cool down I pulled the plug, and expecting to see black (the usual) I saw something way different. It was tan, not white, not black, and this was not a plug chop. It was dry, even the metal on the bottom was clean and dry, before there would be oil on it. I hope I am not too lean somewheres. It ran perfect, scary as a matter of fact, except for the surging thing which it always did. Perhaps the carb is too small for the bike? I mean 250's run 38's. this is only 2x as big, and 1 mm more. I have seen 125's with 39's on them! Somewhere down the road it would be nice to try the 41mm, price is not bad (low 200's) and I think it belongs on there anyways. The temp here today was 68 and dry, I am at around 1200 ft. If I keep the jetting the same I will not run it in colder weather, only warmer or I might try changing the main back to stock (168) if I can get a tool to get it out without removing the carb again. Overall a HUGE improvement!
Thanks Guys,
Rob

[gowen]

Rob, that's awesome. Thanks for the input. I'm still in shock about the surging. But a good shock.

Well, an update on the work: I went riding today, had an awesome time. Rode for 5 hours non-stop. I have to say... I love this bike. It ran soooooo nice. Idled! But, after about 3 hours of riding, I did start to notice that 1/4th throttle was pretty lean. When I'd put the throttle at 1/4th, it would absolutely hit the peak RPM and slide everywhere immediately. But, it was not a healthy REV. It felt very lean and uncontrolable. So, I hopped off and turned the air screw in a full turn. It did not help, but hurt the idle a little. It was ONLY at 1/4th throttle. I'm assuming the needle needed to be moved from the CGK to the CGJ. Then, after another hour, the 1/4th was still lean, the half and full throttle felt like it was not near as powerful. Dial-a-wheelie was not working out so great. I'd really have to full throttle it HARD to keep a wheel up. So, I'm thinking it was starting by the needle diameter. As I have the clip on the 4th. It's been a great day! I had so much fun. I felt like I was riding a 250 for a while, until the lean symptoms came out.

Anyway, only two problems of the day. First: As soon as I kicked it into gear, the clutch cable snapped right at the lever. Anyway, thanks to a lot of bolts and hardware I was able to rig something. Second: I busted a pipe mount again. I'm thinking I need to find a new welder as this is not working out. Keeps busting.

Anyway, thanks for everybodys help. I need to work on my jetting a little, but nothing major. It ran great, except that one spot that was a little scary due to over sensitive throttle at the 1/4th.

Would you guys think it is the needle diameter?

Thanks

[RexRob]

Gabe,
As far as all my research goes it seems that the 500 is a bear to jet, even if you do it can change with the weather. I really don't remember having any problems with my '91, always ran good as far as I know. Too bad you don't have an a/f meter on it, that sounds like it would be invaluable to getting it perfect, you would be able to read the mixture at the pipe. By the way, what color were your plugs? They do tend to give you a lot of info.
Also, and possibly what could help with the surging thing is the slide. Maybe try getting the richer slide, according to Gorr's website here is the breakdown of what effects what:
Closed to 1/8 throttle  air screw and pilot/slow jet
1/8 to 1/4 throttle: air-screw, pilot/slow jet, and throttle slide
1/4 to 1/2 throttle: throttle slide and jet needle
1/2 to full open: jet needle, spray-bar/needle jet, main jet, and air jet
Seems like the slide plays a major role in a variety of throttle openings, dunno, but it's a thought. Maybe sudco has them for $10, might be worth a try....
Looking back through the years, I had almost 20 bikes, and I can still remember my first mx'er 1982 rm 125. That ran perfect from day 1, In the winter in the snow and on 90+ degree days nothing ever phazed it.
Lastly, did you ever try boyesen reeds in it? Or a reed spacer? I think somewhere is the answer to getting the surging solved.
Reguards,
Rob

[KXcam22]

Gabe,
  Glad you had a good day!  Did you try the richer needle or just ride?  Was one mine yesterday, definitely surges worse than yours but I never notice when I'm riding.  Sweet bike, I'll put up with the surges! My boysens and reedspacer don't alter the surging at all (make power smoother only).  I don't think the KX is a bear to jet, but it doesn't necessarily respond as crisp as other bikes.  At altitude (6000'+) mine is the best running bike of the group I ride with. The KTM's barely run. It's fun being able to outstart the e-start bikes. Cam.