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Discussion Starter #1
Hi everybody,

Hoping for some help from people wiser than myself (everyone) to help get me home.

I've been traveling on an 07 KLR for two years now, California to Ushuaia, and back. 45k miles on this trip, although the bike has about 60k total. Now, I'm 450 miles from the final destination (Boston) and it's really died on me. Stuck in Pennsylvania.

Here's the shortest version I can provide:

Bike starts and idles fine. But under load, it cannot maintain high RPMs. Even in neutral, if I open the throttle, it starts to sputter and die above 4k RPM. Can't go above 2k or 3k RPM while riding.

Today, I changed spark plug (ngk iridium), swapped in a spare ignition coil, visually inspected wires for damage, checked that gas is flowing to carb, cleaned main and pilot jets, cleaned air filter, and checked breather and vacuum hoses. All look fine to me. Problem is unchanged.

In cleaning the carb, I notice oil behind the small, air cut off diaphragm on the side of the CVK. Oil in my carb? Which reminds me that it's been drinking more oil than usual recently.

No unusual smoke from exhaust.

Obviously, I'm leaving out a ton of other stuff that's happened since California. That'd be a novel.

Anyone got any ideas or tests I can run on the side of the road? I've been searching for 'oil in carb', but everything seems to be about oil in the airbox. There may have been more oil in the air filter than I expected. But I oil that filter, so I can't say.

Any help is greatly, greatly appreciated. I'm so freaking close to the end. Just want to go home.
 

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That small diaphragm is the decel valve. I imagine it could get oil behind it from oil coming from the airbox. I don't' think that is the main problem.

What you describe are the classic symptoms of bogging under load. That indicates that the main diaphragm may be torn. Remove it, inspect it for holes.

While you are at it, remove the idle et and check it again. You should be able to see daylight through the axial hole.
 

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Discussion Starter #3
Hi Tom,

First off, thank you so much for everything you contribute on this forum. I've been reading your posts for years. Huge fan.

I just out the carb back in five minutes ago. I'd read people mention the large diaphragm as a suspect, so I checked it against a light pretty thoroughly. Looked fine. Couldn't see any damage or light passing through.

Also pulled both jets. No blockage and plenty of light coming through the tunnel. Holes through the sides also clean and clear.

Anything else you'd recommend checking??
 

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The throttle slide diaphragm is my thought also.

Are there any nicks on the outer perimeter sealing lip? Are there any impressions from imperfections on the top plastic cap?
Is there any corrosion in the groove that the sealing lip seats into?

Tucker Rocky / Bikers Choice #482841 TP Keihin Membrane Seal, (Diaphragm) only about $17. Or a complete Harley Sportster CV 40 throttle slide assembly.
 

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A lack of ability to rev usually indicates that the engine is not getting enough air, fuel, or both.

You say that you have checked the breather hose, but I'm not sure if you mean the big rubber hose going from the crankcase to the airbox or if you mean the vent line. If you meant the big rubber hose, then disconnect the vent line at the carb. If the vent line is blocked the carb can't flow gas to the bowl. You could also pull the vent elbow out of the carb and make sure it is clear. Some of the earlier vent elbows were restricted. It wouldn't take much of a critter's crap to block it. I know the '08 elbows were restricted and the '07's might have been as well.

The air filter may be dirty and not flowing air. In your case, that seems simplistic. Still worth checking.

The fact that it runs well at idle would indicate that the ignition system is working fairly well. Usually, they either work or they don't. There is a remote possibility that the pick-up coil's wires are broken, usually down by the case where they exit the case near the front sprocket. Increased vibration may cause an intermittent connection. This is really grasping at straws, but the wires down there do tend to get brittle. If it begins to run rough and sputters a bit as you try to increase RPM then that would support the idea. If it simply won't rev but runs smoothly up to that point, not so much. I suppose that the exciter coil's wires could be suspect as well.

If the slide won't lift it won't have power and won't rev well (most common and why I thought the diaphragm might be compromised). Blast the decel valve passageways with some carb cleaner to clear any oil; perhaps the oil is a culprit here. Again, grasping at straws.

If the floats are stuck in a raised position then the inlet valve won't allow enough gas in to support higher RPMs. Without starting the engine beforehand, remove the drain screw from the bottom of the bowl. At least an ounce of gas or so should come out. You could remove the bowl, gently, and see if they are in the dropped position as they should be when the bowl is off. Move the float up and down to check for free and easy motion.

You say that the fuel flow to the carb is good, but the tank really needs to be able to flow a couple of ounces a minute. Figure it should have a good, healthy stream rather than just a dribble. The stock, vacuum operated petcock, has a couple of extra opportunities to reduce flow. The selector gasket can degrade and block flow and the diaphragm can degrade and reduce flow as well. These are age-related and if the petcock is original then it might be a good candidate.
 

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Discussion Starter #6
Thanks for all the feedback guys. Third test drive of the day, but still no joy.

Short Version: I've tested everything recommended except pulling the petcock. One thing I notice on these test rides is the bike is backfiring more on deceleration than I'm used to. And there seems to be more engine noise up front than I'd expect, compared to at the exhaust.

Could I be looking at a head gasket issue?


Long Version:

I've been over the large diaphragm with a fine tough comb. There's some visible wear, a slight texture to the rubber in some places. But no holes, no cracks or nicks, and no corrosion or malfeasance on the plastic cap or carb itself. Shucks.

Big breather hose (to crank case) and vent line (to carb) are clear, and hold pressure when I block the other end with my thumb. I checked the elbows yesterday when I cleaned the carb, and they also are clear. Also blew out all passages in the dismantled carb while I had it apart. Float moved smooth and easily with gravity as I tilt carb back and forth, and the little rubber tip on the plunger that moves with it is clean and soft, no cracks.

Wires at the front sprocket and to the coil look good. Air filter is spiffy clean, and when I drained gas from tank yesterday (by sucking on vacuum hose) I filled a small soup bowl in a minute no sweat.

Petcock I haven't pulled yet. No place to empty the tank. But it's on the list.
 

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If the petcock diaphragm hose holds suction on your tongue and the fuel screens on both the ON & Reserve inlets can flow a soup bowl full per minute, I see No Reason to remove or dismantle the petcock, unless the automatic OFF is non-functional.

The 'after-fire' out the tail pipe on deceleration and the increased noise Up Front could easily be caused by the same thing, a BAD exhaust Header pipe to head Gasket. Part # 11060-1108. Possibly caused by missing or loose nuts.

Do you have access to a straight edge? It could be possible that the plastic carb top has Warped and that could cause the vacuum loss to prevent full lift of the diaphragm & slide!
 

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I agree with Paul on the header pipe gasket issue, though I don't see how that would affect running. Sometimes simply tightening the nuts will fix that issue. If not, a new gasket will.

As much as I hate to say it, I'm leaning toward an idle circuit issue. That would be the idle jet itself (you wouldn't believe how many 'ok' idle jets wind up being clogged. And, not to put to fine a point on it, the same goes for 'good' diaphragms. These things can be beastly.) and/or the idle circuit passages themselves. There are three small holes at the leading edge of the butterfly plate. These all need to be clear. The problem is that the idle jet hole is less than .015" and the passages in the carb body are not a lot larger.

The saying "... when you have eliminated the impossible, whatever remains, however improbable, must be the truth...". Check the idle jet again, making sure that you can see daylight. Better if you can pass a small wire through.



The passageways in the carb body can be confirmed to be clear by spraying a fluid through them and witnessing that fluid coming out of the three holes.

The idle circuit has a strong influence up to about mid throttle and a bad idle circuit won't let the engine make enough power to pull the hat off yer head.

It's good that you could fill a bowl with gas in a minute. That indicates that the petcock is fine.

By the by, do you have Vaseline, Chapstick, a Thermarest patch kit or any similar sorts of things? Those can be useful to limp a bad diaphragm home. Vaseline or Chapstick can help seal the edge of the diaphragm and hold it in place while the cover is put back. Applied to both sides of the edge that could help if the cap is warped and also ensure that the edge doesn't get pinched.
 

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Discussion Starter #9
Tom and Paul, I hope you guys get a tax credit or something for the time you put in here. The pipe gasket is new as of a few months ago, but international shipping confusion means I have three extras on hand. Will swap one in to be sure. As for jets, I must have learned how to clean them from a prior Tom post, because the wire trick is exactly how I do it. Same with pathways through the carb. Both fine.

Never heard of the Vaseline trick for diaphragms. I'll try that next, although I reckon it's worth buying a new one anyways.

Thanks again. I'll let you know how it goes.
 

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Never heard of the Vaseline trick for diaphragms. I'll try that next, although I reckon it's worth buying a new one anyways.
The Vaseline or grease merely holds the diaphragm in its slot around the mixing chamber while the plastic cap is cinched down by tightening machine screws. Purpose? Insure air-tight seal around diaphragm, with its lip securely bottomed in its circular slot.

"Buying a new one (diaphragm)" may be a larger enterprise than one might think; could be in an assembly including slide; kinda pricey (pricey when purchased from Kawasaki; an equivalent Harley CV40 part may save some money).
 

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In the process of taking the cab apart and re-assembling it you didn't misplace the jet-needle, did you?

It is the silver piece that goes first in the main jet bore, followed by the needle jet holder, followed by the main jet. The tip of it should be visible in the venturi.

It is also called a collar.



 

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Discussion Starter #12
Hi guys,

Apologies for radio silence. I pulled the rip cord and got myself towed home. Currently working on the bike indoors! With lights! And a table!

Unfortunately, still no joy.

I've gone through the carburetor, soup to nuts, twice more. Blasted all passages with cleaner. Flossed most passages and jets with thin copper wire. Overnight soak in carb cleaner for everything metal. Compressed air through everything. And scraped off some dry accumulated gunk from the metal fins on the carb slide diaphragm.

Symptoms unchanged. High RPMs make the bike sputter in any gear. Issue seems to get worse the longer the bike runs.

For background, the main jet is a 148. Fuel screwed backed out 1.75 turns. No 22 cent mod or KLX needle. CA emissions plumbing has been removed. No in-line fuel filter.

I'm buying a new rubber component for the diaphragm, courtesy of Paul's Tucker Rocky recommendation.

But in the meantime, is there any way to validate the belief that it's carb related? Any way to rule out electrical as a culprit? Would a mechanic have diagnostic abilities to help verify this?

For what it's worth, I've chased a minor version of this problem around the bike for the entirety of the trip; A mild bogging under load when air temperature and engine were both hot, and RPMs exceeded 4k. The problem was sporadic, and would disappear for months at a time, making it hard to diagnose. A new ignition coil seemed to help in Costa Rica one time. But when I swapped in another one in Mexico a few months ago, it didn't help Symptoms eased when I opened the choke while driving.

If you read all the way to this, you're a saint. Thanks
 

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Poor performance mitigated by opening the "choke;" suggests fuel-lean running condition. As mentioned, can be caused by diaphragm air leak (insufficient vacuum available to raise the slide and needle).

Yet, looks like you've done everything responsibly possible with the carburetor . . . did you watch the Souperdoo videos (used to be under, "Carb Overhaul" thread on this website; maybe still is).
 

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Found It!!!!!

Guys, thank you all so much for sticking with this thread. And for hammering "lean condition" into my head. I was almost ready to go bouncing around on electrical.

So, after waking up and going through my morning routine (pull carb, clean carb, reinstall carb, fail a test ride) I decided to zero in on the air system. Fuel flows, but does air really blow?

Long story short, I pulled off the rear sub-frame in the hopes of removing the airbox completely and searching for a family of sparrows inside.

Sparrows, no.

Gaping hole where my exhaust has melted through the bottom corner of the airbox, yes!

I'm not sure how to attach a photo to a post here, or if i'm allowed to. But here's a link if anyone's interested. I presume the box is toast and must be replaced. If anyone has any idea how my exhaust came to inflict such a wound, I'd love to hear it and avoid a repeat. Man oh man does it feel good to finally get an answer!

https://photos.app.goo.gl/kcc2KbiZJCpBCKWF9
 

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I sealed an eye shaped/sized hole in the lower front corner of my clean side air box in about 1990 with RTV silicone.
Caused by a Failed exhaust pipe mid-gasket!

But the dust inhalation damage eventually took its toll on the piston & rings and the oil consumption got to 400 miles per pint, requiring a proper top end rebuild in about 2003 & another 20,000 miles.

Here is your proper air box protection, https://www.souperdoo.com/stuff that i think about/melted-reservoir-dog-airbox-too
 

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Discussion Starter #16
Thanks Paul! RTV patch is drying now, built over steel window screen. New aluminum heat shield ready to go in between the box and the pipe tomorrow.

I was planning on doing a 685 kit this winter. Hopefully it lasts til then!

Thanks so much to everyone for all the help! I'll update once it's been test driven.
 

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Discussion Starter #17
Still Broke

I posted this last night, but for some reason, it didn't seem to go public. Apologies if you're seeing this twice.

Bad news :(

After patching the quarter sized hole in the air box, and adding a new aluminum heat shield, my symptoms are better, but still very noticeable.

Takes 2-3 miles of driving before symptoms pop up. Struggling and lurching on inclines and during rapid acceleration. Once the symptoms start, they become progressively more pronounced. At their worst, I can give the bike full throttle and get almost zero new power. Engine feels like it's not firing at all.

I've got a list of things to try moving forward (new diaphragm, new jets, gravity fed petcock, new ignition coil, new mounting boot between carb and engine).

But I'm desperate for some advice on diagnosing what's causing this. Any ideas on further tests I can run, instead of just replacing parts?

One thing I notice is that when I cover the snorkel intake with my hand, the RPMs start to creep up. To me this says that richening the mixture increases RPM, but does that mean I'm lean to begin with?
 

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Where is your float bowl air Vent Hose routed? And is it fully open? I like having the single vent hose running up & over the air duct to the RH side, then over the top of the frame spine to the LH side and hanging along the shock spring.

I once encountered one that the squared tip was resting on TOP of the shock spring adjuster, partially blocking air flow. Cut the tip at an angle, solved the issue. Wow that was over 9 years ago, already.
 

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Discussion Starter #19
Still at it

Hi everybody,

Still chasing this demon around inside the bike, but here's the latest...

VALVES ARE SO TIGHT
Yesterday, I checked valve clearances... SUPER TIGHT!
- Intake clearances were 0.10mm and 0.08mm (spec is 0.10-0.20mm)
- Exhaust clearances were <0.04mm!!! (spec is 0.15-0.25mm)

Would this correlate with my symptoms? I've ordered new shims, and will obviously get this back into spec asap.


EXHAUST
I pulled the exhaust pipe, planning to replace the exhaust gasket (#11060-1108). This went in new in Honduras not so long ago. Shocker. There was nothing left of it. Literally nothing. I thought it must have crushed into place so well that I was missing it, but after crawling around under the bike and scratching at it for a while, I'm convinced that it's just not there. I assembled this myself in Honduras, and I know I put one in. It was the standard OEM copper-looking one. Do these disintegrate?? Both nuts were tight and the exhaust pipe didn't have any wiggle until I loosened the nuts to remove it. What the heck?

I also noticed a lot of very dry, jet black build up inside the exhaust pipe, and inside the engine where the two connect. Not enough to restrict airflow, but impossible not to notice. Does this tell me anything obvious? And should I be trying to clean this stuff out? Swab a finger around inside the engine or exhaust pipe and it comes out black!


FUEL LINE NOT FULL?
I've suspected that the vacuum activated petcock in the tank might be getting stuck, restricting gas flow to the carb. To test this, I removed the plumbing inside the petcock to make it a direct gravity feed. Symptoms persisted. One thing I noticed thanks to a new, clear rubber fuel hose, is that gas does not ever fill the hose completely. Is this normal? There is no in-line filter involved, just a straight 1/4 inch tube from gravity-fed petcock down into the carb. Gasoline fills the bottom few inches of the hose right before the carb, but never the upper section. What to make of this? Something to pursue here?

FLOAT BOWL VENTS
Paul, with regards to the float bowl vent line, I'm pretty sure that's not the culprit. I've routed it every which way at various times, or pulled it off completely. No change. Although I love the trick of cutting vent hoses at an angle to prevent then sucking onto things. Nice!

If anyone read this far, you're probably a crazy person. And I can't thank you enough. Let me know if you've got any advice.
 

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Make sure you checked the valve clearances between compression and power strokes; clearances considerably different there than from between exhaust and intake strokes. (Each at piston TDC.)
 
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