Installed KLX needle- hesitation - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 19 Old 03-24-2019, 09:53 PM Thread Starter
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Join Date: May 2017
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Installed KLX needle- hesitation

Hi fellas,

It's been a long winter but I've had the bike out for a few short rides these last few days. Over the winter I installed an Eagle Mike KLX kit. Bike runs great and I've got a great throttle response, for the most part. However, I'm feeling a very slight hesitation in the 3-3.5 rpm range. It's slight but I feel it there. If I'm cruising at that RPM range steadily, it feels like it almost wants to stumble, and if I blip the throttle when it's there it hesitates ever so slightly. I know a lot of you guys really know your stuff with jetting and I'd like to fix this. Where should I start?

140 main, 1 shim under clip, clip second groove from top, brass washer on top of clip, idle mix screw 1 3/4 out. This is per Eagle mike starting setting instructions.

The slide is drilled, the snorkel is out, UNI filter, stock exhaust.

Thanks for the help.
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post #2 of 19 Old 03-24-2019, 10:48 PM
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Hey JTCrow, I'm in the midst of installing and setting up exactly the same thing. Check out my thread below. I went through the various carb mods one-step-at-a-time and at this point I'm at a very similar stage as you, and I'm working on the exact same issue. For the sake of completeness, I'm putting my process comments in that thread (I'm actually logged in to make more notes there, so gimme a few before checking). Here's my setup so far. It's not perfect (I'm overly picky) but it's workable.

Stock exhaust
Stock airbox
No drill on the carb slide
142 main jet (Not the 140 as suggested… Eagle Mike's KLX kit, purchased in Dec.)
Pilot Jet #42 (Eagle Mike, same time)
Clip at 3rd position on the needle, no shim under
Pilot screw at 2 turns out. Note, the original needle has been swapped for an EZ-just mixture screw from CV Performance (allows easy adjustment on pilot air mixture screw, but has a slightly different profile from stock, which seems like it probably matters — see my thread for a visual comparison)

I tuned the mixture screw today, and I think the above is as good as I can get it without changing stuff. This is at 65° weather, 0-300' altitude.

That being said, I wouldn't take this as "advice." I would instead take it as a note, then wait for pdwestman and Tom to chime in. I'm a novice, they're not. Also, I did a lot of reading on old carb threads here the other day. Try searching for "KLX Needle" or "dynojet" — I found that threads mentioning this other manufacturer's needle were enlightening as background knowledge, and the threads themselves often feature discussion of different needles. I also looked at a lot of harley tuning articles that talk about the CV carb which are, again, interesting background info. You can find these by duckduckgo'ing "CV carb needle" and similar terms.

Here's my thread. I'm curious to see what solutions you come up with!
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post #3 of 19 Old 03-25-2019, 09:52 AM
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I would try the 142 main, 2nd position with no shims. What's your throttle position at the rpm's noted? .....if it's low, you may want to add 1/4 turn or so on the fuel screw or, if necessary, go up one size on the pilot. Beyond these guesses it's AF meter time.......but most of us have had success with the common formula.


Dave
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post #4 of 19 Old 03-25-2019, 10:17 AM
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JTCrow, My suggestion might be to install a #42 pilot jet to slightly richen the 1/8 - 1/4 throttle area & remove the shim from under the needle to keep the 1/4 - 1/2 zone from becoming too rich.

The pilot jet flows fuel from idle to redline. But in diminishing proportion of total volume.

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #5 of 19 Old 03-25-2019, 11:13 AM
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I tend to agree with Paul. You are chasing a very slight issue, one that many would simply throttle through, laughing hysterically and collecting bugs in their teeth.

I think close attention to the idle circuit needs to happen. You ought to use the idle mix screw tweaking method to get the optimal idle mixture, then go just a tad rich. Optimal air/fuel ratio is (well, was, back when gas was gas) 14.7:1. I find that the engine runs best at 13:1, so go a tad rich from the optimal point. All this after a #42 jet, though. The stock jet works OK for the lean condition the factory wants, but it's a tad wimpy for trying to run near 12/13:1.

This guy does a fair job of explaining it: https://www.thejunkmanadv.com/how-to...djustment.html

Once that is behind you then you can play with raising the needle or enlarging the jet. Needle raising should be done (as tedium temendi as it is) a half-groove at a time.

I do have one question for you: What has your gas mileage been?

Tom [email protected]

“She went out slowly. The way she did it hadn’t been learned at business college.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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post #6 of 19 Old 03-26-2019, 11:47 AM Thread Starter
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Thanks guys, hopefully I can get some time to tinker on it and get out for a ride Friday. I'll report back.
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post #7 of 19 Old 03-27-2019, 10:38 AM
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Before you put further labor time, simply pop the snorkel back in and see what happens.
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post #8 of 19 Old 03-27-2019, 10:48 AM
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Quote:
Originally Posted by flexiflyer View Post
Before you put further labor time, simply pop the snorkel back in and see what happens.
Why would one want to do that?

One of the best & simplest ways to improve fuel mileage and engine performance is to allow the air intake to breath easier, then adjust the fuel accordingly. Much more effective, less expensive & quieter than playing with exhaust.

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #9 of 19 Old 03-27-2019, 11:03 AM
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Well, because in less than five minutes without a wrench he will know if he truly has a lean stumble or something else.
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post #10 of 19 Old 03-27-2019, 03:00 PM
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I've been doing a lot of reading these past few days about carb tuning in general, and about the KLR in particular. Seems like there's a lot to be said about the subject. It's interesting how different tuners have different approaches, and there seems to be some variety in what people report as their preferred recipe for the main jet, clip position, pilot jet, and idle fuel screw mixture adjustment. I don't have specfic advice to offer other than to report that by taking a symptoms-based approach and weighing different options, and resisting the desire to make (a) big moves, or (b) different moves in combination (i.e., by experimenting in a methodical way), I am seeing improvements. It's time-consuming to break everything down, make a small adjustment and then go ride again. I guess it would be slightly faster in a proper tuning environment, like on a dyno, but it would still be tedious… shortest time I've achieved from start to finish for such an adjustment is 1 hour. But then again, I work with care…

Here's something interesting: The Clymer book has a great section on the function of the carburetor. It describes the pilot jet as being 0-1/4 throttle, the needle from 1/4 to 3/4, and the main jet from 3/4 on. I feel this straightforward, comprehensive write-up, paired with the more anecdotal writing available online, is helping me understand what's what.

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