New question, the Air box - Page 2 - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #11 of 30 Old 07-31-2019, 05:00 PM
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Here's the image I sought:


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post #12 of 30 Old 07-31-2019, 07:48 PM
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Something I have wanted to ask for a while. Does the L-mod require a clip position change?
Specifically I have a 2016 (Gen 2) with Std exhaust De-snorkeled KLX needle with clip in 2nd groove & the jet to go with it. If I do the L-Mod should I change the clip position?

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post #13 of 30 Old 07-31-2019, 09:19 PM
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Originally Posted by Grant S View Post
Something I have wanted to ask for a while. Does the L-mod require a clip position change?
Specifically I have a 2016 (Gen 2) with Std exhaust De-snorkeled KLX needle with clip in 2nd groove & the jet to go with it. If I do the L-Mod should I change the clip position?

Thanks
Grant
I'll suggest probably NOT.
Unless you are normally at less than 500m above sea-level (go 1 shim richer) or more than 2000m above sea-level (go #1 groove + 1 shim, leaner) .
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post #14 of 30 Old 07-31-2019, 09:28 PM
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It is my understanding that the taper of the needle and the size of the needle jet are DONE by 7/8ths throttle.

So the Main Jet has full control by 7/8th throttle and if the main jet is TOO Rich it feels like the engine pulls harder if one 'Backs-Off' the throttle "just a hair", when revving to near Red-line. This drops the taper of the needle back into the Active 7/8ths zone.

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post #15 of 30 Old 07-31-2019, 09:37 PM
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It's my understanding that popping through exhaust is caused by a lean condition, but a rich condition can result in its more violent cousin, backfiring. Not sure if this can — or does — happen with the KLR, given that most of them run super lean, and then many lean them out more by opening up the intake and exhaust, but it's perhaps worth a mention because in closing up the hole in your airbox you restricted the airflow, and less air flow = richer mixture. If you're way, way rich on the jetting, perhaps that could be related. I'd be curious to hear:

• What pilot jet you have
•*Your idle fuel mixture screw setting
• What needle you have
• What main jet you have
• Whether your carb is clean (what's the recent driving history? Consistent driving with good performance and this just cropped up?)
• How does your bike run in general? Does it feel powerful/smooth/responsive?
- Does it idle at the same speed always or does that move around?
- How does the bike react when it's warm and you open the "choke?"

I will say that I recently experienced a super rich condition when taking my "tuned for power and smoothness at sea level (i.e. damn rich)" bike to 7000+ ft. I don't recall getting backfiring, but did have a host of other symptoms (bike dying at idle, laggy feel on the accelerator, general rough running, super smelly exhaust) that I addressed by lowering my KLR needle and stepping the pilot jet down. I would suggest taking inventory of other factors like these — are there any other changes in how the bike is running overall?

Here's my favorite tip to keep in mind when thinking about fuel mixture. Temperature of the engine has a huge impact on how the carb works. Obviously, OK. Well for me it was news to learn the reason engines need an enricher circuit: because fuel evaporation is a big part of carb operation, and because fuel in a hot environment dissipates into smaller particles more readily than in a cold one. Increased dissipation allows a given volume of fuel to burn more readily, owing to increased surface area of the fuel itself when it's spread out amongst a bunch of small droplets as compared to larger ones. This is why we have to dump extra fuel in a cold engine to get it to start, because the normal amount doesn't burn as well due to the fact that it's "clumped up" — i.e., because the mixture is effectively lean.

Alright skip all that and consider this: At startup, because it's cold, your engine is effectively running lean. Then as it gets warm, the mixture effectively enrichens. As it gets hot, the mixture gets effectively richer still. So, if you're wondering about jetting and where you are compared to where you want to be, you can get valuable clues by taking note of how the bike runs as it warms up. If it's running better (by your judgement, whether "better" means more power, less popping, smoother operation, etc.) cold, it's likely that your jetting is rich because your engine is effectively running lean when cold. Same vice versa: If your bike runs better in stop-and-go traffic, your jetting might be lean, because the bike is effectively running rich. I say "might" because, surely, there are other things that go into how the engine is running at different temperatures (things I really don't know about), but I personally found this to be a very handy way of working with carb settings (and not blurring the picture by messing with more than one thing at a time).

The same thing applies to air temperature. Good cold days can indicate that the jetting is rich. Good super hot days can indicate that the jetting is lean (if the goal is to run well on "normal" temperature days, anyway). Altitude and humidity also go into it. For all three of these factors (temperature, altitude, humidity), "higher" results in "effectively richer."

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post #16 of 30 Old 07-31-2019, 10:39 PM
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Quote:
I'll suggest probably NOT.
Unless you are normally at less than 500m above sea-level (go 1 shim richer) or more than 2000m above sea-level (go #1 groove + 1 shim, leaner) .
Actually my bike lives about 2m above sea level and most of my riding is less than 100m above sea level, so I will keep this in mind when I get around to doing my first non-reversable mod. (cutting 4 one inch holes in the air box lid) Non reversable in the sense that every other mod I have done so far I have the original parts to put back in should I desire.
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post #17 of 30 Old 07-31-2019, 11:37 PM Thread Starter
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I appreciate all the input and information, I just haven’t had the time to even get close to the bike in the past couple of days. I’m sending my daughter off to college in less than two weeks, lots to do, a place to live, car, and everything else she needs to get out on her way. She’s my youngest child and this is really taking a toll on me, this is so much more difficult than I ever imagined it would be. She thinks she is so grown up, and all I see is that little girl running around in a diaper carrying her bottle and old beat up teddy bear.
Anyway I’m hoping to be able to dig into the carb this weekend and hopefully can provide some useful information.
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post #18 of 30 Old 08-01-2019, 09:39 AM
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Originally Posted by Damocles View Post
Good points, but . . . I thought the needle was essentially retracted completely from the main jet at wide-open throttle, where maximum horsepower readings register.

If the needle extends into the main jet at that point, I stand corrected, and understand how the entire needle profile affects mixture (even though the "Care and Feeding" diagram shows the main jet dominating mixture at higher throttle openings).

(I'd post the diagram (Again! ) but I'm into what I hope is momentary computer problems.)
Yep, a valid thought. It's true the needle taper has minimal impact above, say 90% throttle....but the stock jetting transitions from overly lean to overly rich at WOT so you are correct in pointing out the KLX jetting is leaner at WOT (when the needle diameter and taper no longer have an impact).....but running too lean OR too rich can hurt power production. I think people mistakenly think the KLX kit richens the mixture everywhere but it really straightens the mixture curve out. My guess is that the KLX jet kit makes more peak power because the stock WOT jetting is too rich.

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post #19 of 30 Old 08-01-2019, 05:40 PM
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Originally Posted by samuel View Post
... a rich condition can result in its more violent cousin, backfiring.
A rich condition can result in popping through the exhaust, but typically it's accompanied by an air leak in the exhaust system.

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post #20 of 30 Old 08-01-2019, 08:47 PM
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Originally Posted by Norton 850 View Post
A rich condition can result in popping through the exhaust, but typically it's accompanied by an air leak in the exhaust system.

Jason
Jason,
On Gen 1's, it is usually "too lean"of mixture on the low speed circuit which can cause 'after-fire' in the exhaust. Therefore the 'Idle air cut-off valve' diaphragm on the LH side of the carb.
This is applicable to Gen 2's which have had the "Air Injection System" removed also.

But on a stock & standard Gen 2 with the A.I.S. still installed, they will pop more severely than a Gen 2 with the A.I.S. removed. (Essentially a purposeful air leak, for emissions reasons.)
The stock & standard QUIET muffler does a very good job of damping the popping! With a louder aftermarket muffler one will hear the 'full report'!
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