jetting-confused

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Matt-itude
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jetting-confused

Post by Matt-itude »

ok 03 kdx 200 woods pipe. vforce 3 reeds. timing advanced. snorkel removed. 12t counter sprocket. I run usually at 5500ft up and have #148 main #40 pilot a.s. @1 1/4 turns with a cem needle. stock carb and silencer. the thing is at 8500-9000 ft with the stock needle and these jets it would get hot at light throttle positions about 1/8 to 1/4 (slightly to lean) so I put in the cem and the running hot is curred, but I have to run this needle in the leanest (top clip position, needle lowest in the slide) to keep my throttle response from being a little sluggish (feels a slight bit rich). am I missing something somewhere or should I try the cgm or cel needle? it only bothers me because lots of people seem to get the cem to work well and I don't recall anyone using a cgm to be close to the middle of there adj on the needle.also it seems most people report using the cel with modified carbs and slides. mine is stock. bought the bike new and the slide is stamped 5. Love to get a little input from the experienced ones here. Thanks in advance!
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Post by Indawoods »

Where are you getting these funky needles? :shock:

I only recall the CEL working OK with a stock carb.
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Post by Matt-itude »

when I decided on needles I compiled all the needles I read any where on the net and took a SWAG (super wild a** guess) at it. so mabey that is all I needed. I'll work from there. thank you much. Ill post back on my findings but I guess you already know. :prayer: :prayer:
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Post by krazyinski »

I just installed a CEM 2nd from the top on my 220 with 155 main 45 pilot at 700ft 90 to 100 deg temps and it runs perfect.
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Post by canyncarvr »

A CEM has too large a diameter on clip one has a very late taper start.

I've not run a CEM because it's too far off base (imo) to even consider. A richer diameter with an earlier taper start would seem a better choice to me.

The larger majority of riders like the CEL with the #5 slide...and that probably on clip three or four.

Still, what works for YOU is what works!! I am in no position to say the CEM is all wrong..just different from everyone else.

Have you tried a CEL?

Part of it is the woods pipe. It runs quite a bit richer than the rev does. I could change from my rev to a woods (torque), change nothing in jetting and change from good jetting to fouling plugs.

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Post by Matt-itude »

OK I do have a CEL in my collection. The reason I didn't ask about it was I am as lean as I can go with the clip position and a CEL will be one step richer in the 1/8 to 1/4 throttle on the charts. I arrived at the leanest clip position because it was sluggish to respond in all but the leanest position. That was why I had asked about the CGM needle. So with my setup would going to the CEL and down one on the pilot to a 38 help me with the rich bottom end and keep it clear in the mid throttle positions? It just seems that my pilot is getting down there in size.
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Post by canyncarvr »

I'm getting the idea that the 'Thanks in advance' part of your post isn't going to work well this time. :wink:

Your bike seems a good bit 'out of whack' for some reason. A 148 is pretty little. I stuck my bike with a 148...that was @3500'. Granted...an anecdotal tale of woe that has no wide application..but I'd be concerned with using a 148 unless I had made darn sure it was right. It would certainly be better suited @5500'+...still, my WAG is a 148 would normally be a bit lean.

Any 'E' needle on clip-1 is suspicious. That is a shorter (L1) needle than OEM, still the first clip seems pretty severe to me. It doesn't fit at all into JD's spreadsheet against a couple other needles I know work well.

Take '..throttle response sluggish..' so you figure it to be rich.

It's common to have an off-idle throttle response problem cured by turning the air screw in (more rich).

re: 'it would get hot at light throttle positions ..' Timing obviously effects that...and you have changed yours. Changed to what, by the way? How much? It takes only about .050" movement on the flywheel to make a single º change. The stator being smaller in diameter, it would be a lesser movement-per-degree.

I've been back and forth on timing on my bike...decided it ran best where I started.


Any chance your VForce is upside down?


Any chance the KIPS is damaged or not working for whatever reason? Just 'cuz it's fairly new sure doesn't mean its OK.

Sorry...I have no itent of impugning your deductions or your mech skill. While no two bikes are the same and reasonable differences in jetting 'requirements' are to be expected, your situation seems far enough off to start looking at some other 'stuff' that maybe has been assumed to be fine when it's not.

Oh...'snorkel removed'. Lid still on? No holes in it? I don't know you will ever get the bike to run well with that much restriction...I don't care how small you jet it. At 5500'+, you need all the air 'volume' you can get!

Are you a 'saturate, squeeze dry' filter guy? That's a problem in search of a solution.

I'm sure there IS an answer to your bike's response/heating situation. I'm not sure the more common jetting suggestions will fix anything.

I'd sure like to hear about it when you get it sorted out, though.

Good Luck!!

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Post by Matt-itude »

Ok im going riding this weekend. I have a good variety of jets and a few needles. I'm definitely going to give my CEL a try (it is still new in the wrapper). So since it seems to run crisp and nice right now should I follow the old one thing at a time or do I need to step my pilot up (do you suppose)? I just don't trust that it would need to be jetted different than everyone elses bikes and I have no more adjustment on the needle which for whatever reason bothers me. Oh for the record the over heating issue was happening and was resolved before I advanced the timing. The advanced timing did give it considerable more bottom end snap too. Well I'm going to go start gathering spark plugs jets and a needle or two. correct me if I'm wrong but the only difference between the CEM and CEL is the diameter. So this should only change the smallest throttle openings. Right?
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Post by canyncarvr »

Something to keep in mind about needles....

CEM and CEL do have different diameters. The L1 of both is the same.

BUT...an L1 of any needle is the length of that needle from the clip end to the place on the taper that the needle is 2.515mm diameter. It is NOT the length of the straight section of the needle!!

Now..you tell me how that fact is going to effect where that taper starts WHEN using a smaller diameter needle.

Aha! It's different, 'eh? :wink:

This fact doesn't matter a whole lot when changing from one diameter step to the next with a given slope and L1. The effect in either case (where the taper starts and the diameter) does indeed effect lower throttle openings, up to 1/4 throttle says JD's spreadsheet.

'One thing at a time' is always a good idea. It gets tedious sometimes, though.

Your 40 pilot could probably lose one size @5500'.

What about the VForce orientation? Humor me! :wink:

Don't let anyone tell you what works best in your bike, where you ride. Your jetting is odd, that doesn't necessarily make it wrong. Sometimes it's easy to be comfortable where you are...so you stay there. That precludes finding out where you should be via some experimentation.

Let us know what you find out!!
Last edited by canyncarvr on 02:02 pm Apr 21 2006, edited 1 time in total.

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Post by Matt-itude »

The Vforce is in right, to look down it it points into the case and lines up. I do remember looking at it when I first got it and wondering though. I work in a shop so you wont insult me by fair questions or some humor. I have solved many problems just having people ask you questions. That makes the old thinker think. I am just wondering if I think it runs good now if it might not run that much better (this is my first KDX)? Talk to you all next week.
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Post by canyncarvr »

OK. I'll try to limit the UNfair questions and complete lack of humor, then.

I mean...I wouldn't do that if you didn't ask..but I'm an obigent (that from ms. malaprop) sort...

The KDX is a very capable woods bike..and it has some performance tweaks lurking, too, that are quite surprising!

Have fun!!

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Post by Matt-itude »

ok the main reads on a plug chop right on the money at 75 and 5500. the pilot and needle however after driving around in just the lower throttle ranges come back rich. I will now go down on the pilot and assume that too rich of pilot is why the needle came back where it did as far as throttle response. oh and a 2/3 wore out rear tire makes my little kdx almost helpless (unless I get to third gear or better) on the dunes with my 205 ish weight.
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Post by canyncarvr »

That's a 148 main? Describe 'right on the money'?

If a 148 is good for the main, that does fit with a 40 pilot being too rich.

Wore out tire? Meaning the paddles are worn down? Not a knobby! :shock:

A knobby is almost helpless when it's brand spanking new (on the dunes)!

Heck...I run about 20 inches of paddle on the dunes..and it's still plenty slippery! (Go Banshee!!) :wink:

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Post by Matt-itude »

we were doing trails with some sand dunes (yes 2/3 worn out knobbie) :oops: . my buddies old cr goes anywhere even with just a good knobby. and absolutely hauls with a paddle. anyways you are right on on the too rich pilot. just changed the pilot down to a 38 and tried it around the yard (lighter throttle openings) the plug may be dark now but it is not wet down in the bottom around the bottom of the electrode insulator after putting around (it used to be a little shinny/wet clear down in the bottom). so then I put the CEL needle in in the 2nd position (I know everyone else runs 3 or 4) ok this is a good mod I think this gave me as much or more bottom snap, not that I was complaining before, as advancing the timing to the max. mark.(I know you have been waiting for me to spill to you how far I turned that thing). I did of course have the carb off so I looked down my vforce again and yes it all lines up perfectly. It seems that the vforce logo is on the upper left hand side of the cage(if that matters). Any how I am stoked because I just gained a few more ponies in the bottom end for free. I guess being anal and worrying about everyone elses set up on this sight just payed off. I will fine tune the needle position and air screw when I get out again. FWIW my house (testing in the yard) is at about 4500ft. Thanks all!!!
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Post by canyncarvr »

Don't overlook the CEL @ -3 and -4. Just 'cuz you tried it (maybe) before, now things are different...so whatever 'was' before needs to be re-addressed.

At 5500+ el., you could use a smaller head volume. That's the smallest impact of a good machine job on your head..the piston clearance and squish angles matter more.

You need RB's number? :wink:

You've heard the rule of thumb I'm sure...timing advance rarely helps anything, timing retard often does. Timing advance does often result in engine damage. IF timing advance is/would be beneficial the amount of timing change when moving the stator to the end of its mechanical limit is generally way too much in the way of ºs.

That said...whatever works for you!

Have fun riding!!

It would be interesting to know that -3/4 on the CEL in your case is certainly not as good as -2.

Thanks for the update!!

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Post by Matt-itude »

I will let you know when I can go riding again on the needle position. I started at -2 because my bike so far seems to like the jetting a slight bit leaner than most run. I have not yet got to try any other positions on the CEL. Like I said the smaller pilot and different needle are a definite improvement without having them dialed in so... I moved it to the maximum mark not the maximum mechanical limit (the timing). I think Im going to try moving it back now because my bottom end power is exceptionally strong now. Also before when you opened it up it would rev through the power and just when you thought it time to shift it would come into a small like second power band in the high revs. not pronounced enough to feel until you got into 5th and 6th gear on a smooth flat road. I haven't felt that since I advanced the timing, which of course makes sense. I think the KDX may allow me to have my cake and eat it too! :grin:
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Post by Rhodester »

Eric Gorr told me that our engines make so little compression that advancing our timing gives us very little risk of bad things happening. He advised advancing it 1 full marks distance beyond the most fully advanced mark (for a snappier bottom end). I had my cylinder base shaved and my head shaved/relieved and now run 158 LBS of compression (only an 8 LBS increase from before). With that I'm running my timing 1/2 a marks distance past the most fully advanced mark. I have zero negative effects from any of this. I'm currently running a standard Cometic head gasket. When I do my next top end (next year) I'm going to put in a very thin head gasket to further boost my compression and enhance my bottom end.
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Post by Matt-itude »

so rhodester in your opinion do you feel you lost anything on the top. all I know is that my bike has more power on the bottom now than the tire can handle. And with your mods you probably are not running pump gas right?
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Post by Rhodester »

I'm running 91 octane pump gas with no detonation or overheating problems....ever. It doesn't seem like I've lost anything on top at all. If I end up modifying things for more compression it might become an issue (if I over-do it), but so far no negative whatsoever.
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Post by canyncarvr »

Mentioned to fit in the chapter of 'How Things Differ':

Stock head, FRP ported cylinder (nothing removed from the bottom of the barrel), 92 Octane pump-crap, standard spark timing, 15-4500'el....my bike detonated bad enough to blow a KIPS drum completely out of the cylinder. If I don't run toluene or Trick114, my bike will blow up. :rolleyes:

YeeHAw!

A by-the-way...but why cut the bottom of a cylinder to raise compression? There are better ways to do that and NOT compromise/change port timing.

Or...a port timing change was intended? That's not uncommon when 'tuning' say, a KX250 to run in the woods, but a KDX? No..they don't run a lot of compression...they also don't have anything close to 'radical' or even 'hot' port timing.

Rhodester: What is your impression of top-end detriment with your timing increase?

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