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Discussion Starter #1
Here's the latest iteration:

High RPMs highway travel, when its >75* outside, >4000 RPMs, with the 16 tooth front - 60mph indicated or higher, it starts cutting out like I'm running out of gas. Even with a full tank. Its almost like there's a piece of trash or something in the main jet. I've taken the whole thing apart from the tank to the carburetor and its clean. Jets are spotless, no indication of anything in the bowl. The diaphram is intact up top and the seal is still good.

I've just ever so slightly raised the fuel float level and I haven't tried that out yet. The only thing I can think of is that I added the 2nd washer of the 22 cent mod in December and maybe, whatever. That's the only thing I can come up with. What do you think?
 

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I've had a couple of atv carbs that people had forgotten the needle jet above the main emulsion tube & didn't run for crap. Then they found it & installed it.
Then they still seemed too rich/sputtery on main jet even with altitude appropriate main jet.

Some liquid teflon thread sealant on the emulsion tube threads stopped fuel from passing around the threads.
 

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Have you tried riding with the gas cap cracked open? Perhaps the umbrella seals are sticking which would create a vacuum in the tank and not allow sufficient fuel to flow under those conditions.
 
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Discussion Starter #4
Have you tried riding with the gas cap cracked open? Perhaps the umbrella seals are sticking which would create a vacuum in the tank and not allow sufficient fuel to flow under those conditions.
I have not tried that. I will try that, after I try this latest iteration of float adjustment in about 5 minutes.
 

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Gas cap vent would be my first thought too....you don't have an aftermarket fuel filter do you? After that it'd be checking carb and jet installation.

Dave
 

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I have seen some 'rough texture' or imperfections in the sealing surface of a couple of the black plastic Carb Tops which seals the diaphragm vacuum chamber.
If the carb top was rotated the imprint of the imperfection could be in a different location.

If there is any vacuum leakage for any reason from that carb top they usually start stuttering by 4000 and will Not rev over 5000.
 

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Discussion Starter #7
Just completed about a 600 mile road trip on it. I'm convinced its a tank vent issue. The issue starts occurring with about 2 gallons left in the tank and you feel like its hitting reserve time. The last time it happened I cracked the tank cap open and kept on going without needing to be in reserve. So there we have it, its a vent issue. But now I have a new fuel line and inline filter too.
 

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If one uses an empty Visine bottle or something similar to create a vacuum on the fuel tap automatic diaphragm hose or has a manual valve, one could time how long it takes to drain the 5 - 5.5 gallons of normally level accessible fuel like on a flat straight highway.

If fuel flow slows or stops, 1st check that the Visine bottle still has vacuum. Then open fuel cap, if needed.

One could temporarily use empty, clean milk or water jugs to measure time per each gallon. (They are actually larger than a gallon.)

The fuel system needs to flow at least 3 gallons per hour (1.2qt per 6 min) to sustain 30mpg @ 90mph in a head wind. My bike got 35mpg in similar conditions, twice.

Time this once with tap in the ON position & a second time in the Reserve position. (Is there any possible old fuel varnish restricting the internal fuel filter screens?)
 

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Discussion Starter #9
So it did it again today. 60mph and sputter-sputter-fell on its face. 3 gallons of gas left in the tank. While I was still coasting I took the key out and cracked the fuel cap and it fired right up before I even got below 40mph. I just took the gas cap apart and it seems like this first rubber umbrella gets "stickier" as the ambient temp goes up. Blowing through it seems like it takes a little more force than should be necessary for a vacuum to breathe with it. That umbrella seal doesn't show to be its own part on the parts diagram. Guess I'll have to "improvise."
 

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Discussion Starter #11
I'm good. I get more than enough range out of the stock tank before my arse needs a break and my face shield needs a wipe down.
 

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I'm good. I get more than enough range out of the stock tank before my arse needs a break and my face shield needs a wipe down.
I agree wholeheartedly; the KLR is one of the only bikes to come with a large enough stock tank. No, my satisfaction from my IMS 6.6 tanks comes from all the other benefits; no rust, no dents, no paint to scratch, I get rad protection without adding another 15 lbs worth of crashbars, and with my Raptor petcocks, I've eliminated two common failure points (gas cap and petcock).

Dave
 

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Discussion Starter #13
Just to finish up, the gas cap was the problem. Fixed that little seal inside it and the issue never came back. I sold that bike a year ago and bought a CB500X, and now I've sold it and looking to get another KLR. Slim pickens out there.
 

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Similar issue with my '08 the other day. Just filled it up (Probably too much) and about 10 minutes afterwards it starts missing and sounds like it's going to hack up a lung. Harder and harder to start. I immediately dumped a bunch of Seafoam into it and limped home. After checking things over, I took it out and ran the living crap out of it. High RPM's and aggressive acceleration for about 1/2 an hour.
Must have blown some crud out of the carb because it has never run better! Smoother idle, less 'pop' an deceleration, maybe even a bit more power.

I'll be doing that again on a regular basis.
 
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