Leaner needles

[turner]

Hey guys I have tried cel and del needles, but they are all rich on the bottom even with a 35 pilot. This makes starting real hard and it will barely idle with the screw cranked in. I understand that I need a different diameter needle. I saw a chart on ducan racing with the letters and numbers next to it, but what would be leaner.

[rbates9]

Have you checked the jet block gasket and the float height?

I just use a 6 penny finish nail for a needle. Works great!

[turner]

Yes I've checked the float. Hope your not serious with the nail haha

[Julien D]

Does sound like you have another problem going on. Lots of people use CEL/DEL needles and do not have issues with starting/idle. If you look above, at the needle guide, it helps explain what L1, taper, and diameter markings are, and which are leaner or richer.

[turner]

Right so I have a cel and the l means 70. But would leaner be a 68 or a 72? I don't really have an idea if one letter will be enough change. My bike is stock, and the power valve and reeds are good. I had the stock needle, and it would be really rich at high altitude with a 42 pilot. The low idle and hard starting happened when I switched to cel and del.

[Julien D]

The L/70 is diameter. Disregard the 70, that OEM number is just going to confuse you. As you increase diameter, less fuel flows by the needle, making it leaner, specifically from 1/8 - 1/4 throttle. So a CEM is leaner than a CEL which is leaner than a CEK. Likewise, as your L1 length increases, it gets leaner in the 1/4 throttle range. So CGL is leaner than CEL at a very specific throttle position.

To illustrate, here is what the needle profile looks like from CEL > CGM, all else being equal.

CELvsCGM.jpg (192.15 KiB) Viewed 9921 times

And here's what the needle profile looks like going from CEL > CGN.

CELvsCGN.jpg (188.74 KiB) Viewed 9921 times

You can see that L1 and Diameter affect primarily 1/8 - 1/4 throttle. When you are jetting, remember that this is directly related to throttle position, regardless of RPM. So if you get it on the lean side at 1/4 throttle and low RPM (no stutter), then it is likely to be quite lean at 1/4 throttle and 6k RPM. That's why having a slight stutter if you slap the throttle WFO from idle is not necessarily a bad thing.

[turner]

Alright I gues ill order a cek. I measured my stock and del needle just below the clip, that isn't tapered, measured both the same diameter. Or do I measure the diameter at the very top off the taper? I guess I'll just try a cek for now

[Julien D]

Damn, it was early when I posted that I guess. I'll go back and edit it. CEK is going to be RICHER than CEL. As you progress, diameter gets larger, less fuel goes through, things get leaner. If you are after a needle that is leaner at low throttle openings, you'll want a needle with a larger diameter and/or longer L1 length. Look at the top of the jetting guide sheet for where to measure the diameter. All needles of the same series will be the same diameter where the clip goes. The diameter is measured a few mm below the clip section. From stock to CEL you're talking about .01mm difference.

[turner]

So I should look at a cem then? Yeah the cel took out that 1/4throttle bog from stock, but made the pilot circuit way to rich.

[Brian]

I had a similar problem a while back. It had a blubber below 1/4 throttle that got better with a smaller and smaller pilot. I ended up with a #35 pilot. However, the leaner and cleaner it was below 1/4 throttle, the leaner and worse it ran above 1/2 throttle. I checked and changed float height, replaced the jet block o-ring, changed needles and clip positions. Eventually I found that going up a couple sizes on the main jet helped. I have a #158 main and it is running so much better everywhere.

I should mention I have a 220 with the RB mods and a rev pipe.

[kdxtreme]

I had a similar problem a while back. It had a blubber below 1/4 throttle that got better with a smaller and smaller pilot. I ended up with a #35 pilot. However, the leaner and cleaner it was below 1/4 throttle, the leaner and worse it ran above 1/2 throttle. I checked and changed float height, replaced the jet block o-ring, changed needles and clip positions. Eventually I found that going up a couple sizes on the main jet helped. I have a #158 main and it is running so much better everywhere.

I should mention I have a 220 with the RB mods and a rev pipe.

So what kind of milage are you getting with the 158 in there.

[Brian]

I seem to get about 35 MPG no matter what size main jet I use. I think that at highway speeds the engine is running at such a frantic speed that small changes in jetting won't offset the friction of that little engine running at 7000 RPM. However, having the smaller pilot and larger main make it run really clean at part throttle like cruising at slow to medium trail speeds like when your with your kids or other inexperienced rider but still allow the bike to take off cleanly when you wick the throttle wide open, without bogging and caughing and occasionally "flaming out".

[kdxtreme]

35mpg that's really good.

[Brian]

I thought it would've been better but I suppose it is a dirt bike and not geared or otherwise designed for fuel economy. I have done the math and it's still cheeper to commute on than my minivan but not by much when you factor in the cost of premium gas and 2-stroke oil. But then, it's not about the money, is it... When you factor in the "smiles per mile", it's much better on a motorcycle

[turner]

I ordered a CEN today so hopefully I can try it out on Saturday. $7 shipping sucks though haha. Anyone else know somewhere that sells needles for less shipping?

[Julien D]

Where did you order it? I pretty much only get carb parts from jetsrus or psep.

[twowheelfanatic]

did the cen fix your jetting issue?i have a new to me 2000 kdx200 and you are describing my jetting to a t.im not sure which needle i have as im going to check it tomarow.im assuming its a stock needle.from 1/8 to 1/4 with load on bike its pretty rich like choke on.i tried even putting clip on top groove and still sputters but made it really anemic from 1/4 to 3/4 throttle with load.i settled on 2nd groove from top which it runs better from 1/4 throttle up.thanks for any help you can give