Jetting!!! Again and again and again!

[kawdude]

So is the knocking not piston slap?  I'm concerned that it will lock up if I run it that way.  Also, are you able to change the jets and the clip with removing seat, gas tank and carb.  That's what really pisses me off.  The weather hear was beautiful on Sunday also which probably had something to do with it.  It amazed me that 1 notch took the snap away since all the diagrams I've seen say the needle jet doesn't do much until mid...that's bs.  I'll screw with it somemore.  At least, this time I got changes in performance.   It seems to me that my bike is better at 52.  I'd be afraid to try anything smaller, however, the main jet needs to be dropped to 165 at least because when I got on it it fell flat.  I suppose the exhaust valves could be stuck but d**n I've only put around 15 - 20 hours on it since the rebuild.  Thanks for your help!
One other thing...
The bike started on the 3rd kick!!!  Hell, I was still priming it.  No racing rev at the start either.  Next time I do this i plan to change/clean the airfilter.  I've been using a filterskin with oil applied to that also.  It's probably plugged.

[kawdude]

Your jetting saga is interesting reading.

Thanks for reading it!  This is Gowen's work in progress so take anything I say with a grain of salt on the jetting topic.  I really don't know what I'm doing here   !!!

[KXcam22]

Gowen,
  Your bike jetting sounds like a tough nut to crack.  You seem to be always headed in the right direction but not quite getting there.  Frustrating I bet!   I would suggest that you may have to dial in the main (plug chop runs up a hill) first and lean the pilot (get a nice idle) then leave them alone and try some different needles until the transition is nice.  Possibly a leaner needle might be the ticket.  Then you could run the needle higher than you normally do to richen the 1/4-1/2 throttle but it would be leaner (ie thicker straight section on the needle) at 3/4. Also some dumb things would be to check the tank cap vent & petcock fuel flow.  I have had a partial plugged vent that would partially airlock the tank after a few hours and leanout the carb by reducing the fuel flow and lowering the float level.  Have you done the tape thing on the grip and marked the throttle incremants.  It helps to tell which jet a weird symptom is comming from (just tell your friends the 1/4 mark is all your allowed to use when racing against hondas). At 42 on the pilot you may be able to borrow 40 & 38 from a 300EXC owner since those are the stock sizes that they have to take out to actualy make then run (same carb).  It's easy to be an armchair quarterback so feel free to ignore me if I sound off the mark. Best of luck Cam.

[KXcam22]

Your are probably way past this but, I thought I'd mention it. When jetting it is good to set & not touch the float level. 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. On the KX the rib in the center of the float should be parallel (or almost) to the carb body but not past. You will find this matches the stock specs.  Cam.

[gowen]

Kawdude, You do not have to remove the tank and seat to change the needle and carb, I just pull the carb out a bit and remove the cap. This can be done by pulling the air box boot back when the clip has been loosened on the carb then popping the carb right out. Pretty simple and saves time. From what I've learned, there is NO substitute for correct jetting. As in, you will get the MOST power out of correct jetting, so if you find more power in the 2nd notch, I would keep it there and keep on working around it.

KXcam, I have tried the float height, but I will try it again, d**n I wish I knew what type of needle I have, then I would go a slot leaner. I know this for sure, when I'm on the 1st notch I'm DEAD lean. No wheelspin and the throttle acts like it is running out of gas, racing the engine.

Ah yes, the notch in the grips, I sure did it. Great idea, which has helped me ALOT in the diagnose of lean and rich mixtures. The problem currently is, I'm juggling the low and mid range, gaining one and losing the other. I did a plug chop on a 162 and it came out dark grey around the BASE of the insulator. Assuming it is rich, I just started running 50:1 using MC1. So, we will see how this works out in a plug chop. The only place I can do a chop and really keep the throttle pinned is either at my Grandparents in Virgina which is like 4 hours away or the place I mentioned above, but is costly just to jet and takes an all day trip, which time is very scarse at my job.

I have to take my KX to the machine shop for a new exhaust mount as it broke not one, not two, but all three mounts. And they were ALL together and fine last ride. So, that will consume my free time. I'm having trouble locating a 158 main jet. Nobody around here has them. I've never thought about a KTM dealer, sounds like a plan for the pilots, as people here are like asking if I  am running a moped or something like that.

My main feels pretty dialed in, but I understand the chop test. That is something I will take care of next. I will pick up the 40 & 38 next.

Help me out here for a second, I'm needing to know what needle to order for the next step leaner, it sounds like a plan but will need your help as I have NO idea how to read a needle, even after reading the justkdx report, it just confused me.

My needle reads: R1366N what would be the next step leaner?

Thanks Cam! I appreciate it. Same to you Kawdude, maybe all this info will get both our bikes screaming.

Btw, it is a spark knock from either the bike running too hot or the fuel not buring correctly (too rich usally), sometimes the timing off, in this case it sounds like a fuel issue (directly related to jetting) Anyway your engine would only be at stake cause it is a lean mixture.

Thanks for the help guys.

[KXcam22]

Gowen,
   Your bike is a '90 right?  The R1366N is an OEM number, its likely that Kaw used this number before switching to the N82M type numbers that are stock in my '92.  It's possible they are the same but hard to tell.  The R1366N works out to a Keihin CGG.  Check out sudco.com catalog under the N, they have a listing for Keihin PWK39 needles.  That R number sounds a lot like the one in my old '87 CR500 (same carb).  Is there any chance your needle is not stock?  If you can't confirm it, it may be prudent to buy a N82M stock needle as a starting point.  I think my old CR had a R1366N and it used a 40 pilot.  It must be a hastle to not have a good jetting place.  Any rural gravel roads in your area?  Take a few runs then take off before any heat arrives. I can post the list of '92 option needles from my manual if you need it. Cam.

[gowen]

Hi Cam, it's funny, I just got off the phone with Sudco. I told them I need a larger diameter to lean out the 1/8-1/4 throttle. Hopefully not effect the mid-top range. The person at Sudco was very helpful in helping me design a needle that would work in the direction I led him. So, I ordered 3 needles, one a step leaner, one another step leaner, and one two steps further. Just incase. I also ordered a 40 and 38 pilot along with a 158 main.  All ended up not being much over $20! Which is down right amazing, so I overnighted it, so I would have it by the weekend. I'll let you guys know how it works out. I'm assuming this will work. I hope so.

[KXcam22]

Gowen,
  Glad that they were lots of help.  This was years ago, but I once put a 38 mikuni (I found it) on my maico race bike. I phoned sudco and they told me the exact jetting I needed (what they sold as their maico carb kit) over the phone. Worked perfect first time. Just for info what letter needles did you get?  Cam.

[kawdude]

Btw, it is a spark knock from either the bike running too hot or the fuel not buring correctly (too rich usally), sometimes the timing off, in this case it sounds like a fuel issue (directly related to jetting) Anyway your engine would only be at stake cause it is a lean mixture.

Thanks for the help guys.

Interesting.  The bike wasn't hot but the timing could have moved, I'll check that.  If I remember correctly, it knocked at 2nd clip, 52 slowjet and surged terribly.  Removed the idle surging by cranking the air screw in thus removing air and making it richer.  I think I'm a half turn out.  Doesn't this "half turn out" say that the slowjet is too small?   Also, wouldn't idle real well so cranked the idle screw in.  I'm won't argue but why would the engine knock if rich?  Maybe knocking is a not good term...how about aluminum rattling quickly against aluminum.
   
d**nit, I have to read my previous post so I know what I did.

A little off topic but thumpertalk has good prices on jets and seem to carry all the sizes.  I'll be interested in how the Sudco stuff works.  Thanks again.

[kawdude]

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.

JFC!  That's a great idea!  So simple...  

[gowen]

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.

JFC!  That's a great idea!  So simple...  

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]

Just for info what letter needles did you get?  Cam.

Just got the jets in.   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.