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Discussion Starter #1
OK so I bought an 2009 with 1000 miles. The guy had fitted a moose jet kit (155 main / adjustable needle) also fitted was a FMF power bomb with a Supertrapp slip on. He had also hacked a portion of the air box of.
The bike ran fine, but was sucking down the fuel (38 to the gallon). I purchased this as a commuter so I was looking for far better gas mileage.
To gain the fuel mileage I have put everything that was moded back to stock. Original complete exhaust and muffler, replaced main jet with Kawasaki recommended 145 main and 40 pilot, stock none adjustable needle and new plug. Now I am getting about 52 miles per gallon.
HERES THE PROBLEM. When the bike is between about 4000-5000 rpm I get a very slight stutter. If I get up to my normal cruising speed of between 65 and 70 on the interstate it just will not run smooth. It is not major but just enough to annoy me. If I accelerate up to 80 it does not do it but as soon as you ease the throttle back to cruise, it starts again. You also feel a slight stutter when accelerating hard in most gears but seems to be the worst at between 4000 and 5000 rpm.
The only thing that I have not put back to stock is the big hole in the air box (could that be the issue?) It will also give an occasional chuff out of the muffler if you coast down to a slow speed in a high gear without shifting down.
Anyone got any suggestions?
One other thing I noticed is that when I replaced the needle, I noticed that the slide diaphragm seemed to have swollen just a little as in order to get it to seat in the grove I had to use grease (kind of like an o-ring that refuses to sit in the groove due to swelling.
It is not the gas cap vent as I have tried running with gas cap open to no avail.
Thanks again for any suggestions.
 

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IIRC that Moose kit was a relabeled Dynojet kit which is way, way too rich; I'm not surprised at your mileage. Returning it to stock is fine and obviously helped the mileage issue but you can also use the DJ needle with a KH 142 main and it will run perfectly fine (though you still may not get the mileage of the stock, EPA mandated needle). This setup (2nd clip, no shim/spacers, 2 turns on the fuel screw, modified airbox and aftermarket silencer) is exactly what I have on my 2001 and it runs like a top.

Anywho, as far as your current issue, my best guess is that they drilled the slide 1/8" as per the kit's recommendations and that's the cause of your surging/bog. If not, the airbox is certainly the biggest bottleneck in the KLR's "airpump system" so running a less restrictive airbox with the stock jetting (main + needle) could also be causing a problem. Try using some duct tape and cardboard to cover the L mod and see what happens.

Also keep in mind that all jets are not created equal;





Cheers,
Dave
 

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Discussion Starter #3
When you say they might have drilled the slide. What exactly do you mean? At this time I think I will start by taping up the hole in the air box, and see what that does.
 

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"Drilling the slide" means enlarging the vacuum port, the vertical "hole" in the slide connecting the venturi with the volume above the diaphragm. Take a look at, "22-cent mod" for more details. The purpose of drilling the slide (enlarging vacuum port) is: Promoting faster throttle response.

7/64" appears appropriate for KLR650s; 1/8", though common with Harleys, may cause some slide flutter on KLRs.

Back to your problem: Maybe nothing's wrong with the hole in the slide; the problem may be from a fuel-lean condition at mid-throttle. SHIMMING your needle, I'd recommend ONE # 4 washer (some say, "TWO") under your needle, this procedure will fuel-richen mid-throttle mixture somewhat, perhaps curing the problem ("22-cent mod" research discusses needle shimming).
 

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My bone stock KLR had the same peck at cruising speeds ( around 60mph). Slightly shimming the needle up with no other changes cured it.
 

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Yep, to verbalize my thoughts more coherently;

- the stock jetting/needle is overly lean at certain throttle positions. Your airbox mods could be exacerbating the problem by further leaning the mixture. You can try returning the airbox to the stock configuration, shim the needle as suggested (22 cent mod) or just jet properly with the superior DJ needle already in your possession (your mileage issue was because you were so rich, not because of the needle)

Cheers,
Dave
 

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Discussion Starter #7
Thanks for all the suggestions guys. Last night I put some good old duct tape over the massive hole they had carved in the air box. trying to create the size of the stock hole, and she now runs smooth as a babies bottom.
All stuttering has gone. I'm going to fab up a cover using some shim stock and a little silicone.
Never thought that would make such a difference.
Thanks again I'm a happy camper:character00201:
 

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Thanks for all the suggestions guys. Last night I put some good old duct tape over the massive hole they had carved in the air box. trying to create the size of the stock hole, and she now runs smooth as a babies bottom.
All stuttering has gone. I'm going to fab up a cover using some shim stock and a little silicone.
Never thought that would make such a difference.
Thanks again I'm a happy camper:character00201:
Those stock air boxes can be found on ebay. Just a thought if ya wanted one in stock form.
 

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Glad I never swiss cheesed mine.

De-snorkeled seems best for anything under a full
stage two breathing upgrade.
 
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