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Discussion Starter #1
About 30 minutes ago, my bike's engine died while I was waiting at a stoplight. I put it into neutral--which I usually have to do to start it up, anyway--and was able to get it going, but had to constantly hold the throttle open to keep the RPMs from dipping so low that the bike died. I called a friend who knows bikes pretty well, and he thinks the most likely culprit is an obstruction somewhere in the fuel line. What do you think, guys?
 

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Hey Cabron. I like to do the simple and easy first. Because I'm simple and cheap. First thing I would try would be to drain the carburetor float bowl. It is a gathering place for moisture [water], and any other contaminants that might find their way into the fuel delivery system. I won't disagree that there may be a fuel restriction somewhere, however, in light of the information that the bike will run off of the pilot circuit [idle circuit], I doubt that is the issue. I am, however, frequently wrong. Clean out the float bowl first. Now start it and see.....

I know of many bikes and ATV's that run like crap on high alcohol content fuel, known as "ethanol". E10. My bikes all hate it. I shop for alcohol free gas or at least real low alcohol content. My KLR will quit running, act like it has water in the gas, won't idle, cut out at road speeds. Kill and until I drain the bowl and start fresh, won't start. If draining the bowl clears up the issue and it repeats itself, you may have a bad load of gas. Gas and water will separate. Usually in the float bowl.
 

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About 30 minutes ago, my bike's engine died while I was waiting at a stoplight. I put it into neutral--which I usually have to do to start it up, anyway--and was able to get it going, but had to constantly hold the throttle open to keep the RPMs from dipping so low that the bike died. I called a friend who knows bikes pretty well, and he thinks the most likely culprit is an obstruction somewhere in the fuel line. What do you think, guys?

I like to do the simple and easy first also. Try turning up the idle, should be >1200 rpm usually.
 

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this happened to someone I know once. The choke (enricher) accidently
got put on.

kb7tgr
A mere jiggle of the "choke" (enricher) can kill a KLR at operating temperature (How do I know this? Long story!).

In Cabron's case, I agree with Spec; first, adjust the idle speed screw. vatrader's tips on draining the float bowl appears good maintenance practice.

Cabron, ever adjust your fuel screw (behind the tamper-resistant plug in the front bottom of your carb)? Might need to open it up a bit; you might need a tad fuel-richer air/fuel ratio at idle. 1.75 turns out from a soft bottom's a good starting point for a stock engine.
 

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About 30 minutes ago, my bike's engine died while I was waiting at a stoplight. I put it into neutral--which I usually have to do to start it up, anyway--and was able to get it going, but had to constantly hold the throttle open to keep the RPMs from dipping so low that the bike died. I called a friend who knows bikes pretty well, and he thinks the most likely culprit is an obstruction somewhere in the fuel line. What do you think, guys?
A couple east things to check:
1 Air filter
2 fuel filter
3 clean the battery connections

There are a lot of things that "can" cause issues so might wanna let us know, milage, pre or post 08, has the bike studdered or stalled before and the weather conditions when it happened. If you have a dry and clear bottle or glass you might try pulling the fuel tube and pouring some in the container to see if water settles out.
 

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3 clean the battery connections.
Disagree with inadequate battery connections as a possible cause of the problem, Buildit: Ignition and battery circuitry are totally separate on an '01 (thread title indicates model year).

'07 and earlier KLR CDI's (capacitive discharge ignitions) are powered entirely by alternating current from exciter coils of their alternators, not from battery voltage, AFAIK.

'08's and later KLR's have no CDI's; their inductive discharge ignition systems are powered from their battery circuits.
 

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Buildit: Ignition and battery circuitry are totally separate on an '01 (thread title indicates model year).
See the obvious escapes me sometimes.:) I'm just suggesting things the owner might not have thought of. Like checking the spark plug boot to see if it is arking causing a loss of power?
 

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I'm just suggesting things the owner might not have thought of. Like checking the spark plug boot to see if it is arking causing a loss of power?
Good maintenance/trouble-shooting approach, as is checking battery terminals. Also, the GROUND connection (i.e., battery negative terminal to frame) may be critical; perhaps important to ALL model year KLR's.
 

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Discussion Starter #11
Hey Cabron. I like to do the simple and easy first. Because I'm simple and cheap. First thing I would try would be to drain the carburetor float bowl. It is a gathering place for moisture [water], and any other contaminants that might find their way into the fuel delivery system. I won't disagree that there may be a fuel restriction somewhere, however, in light of the information that the bike will run off of the pilot circuit [idle circuit], I doubt that is the issue. I am, however, frequently wrong. Clean out the float bowl first. Now start it and see.....

I know of many bikes and ATV's that run like crap on high alcohol content fuel, known as "ethanol". E10. My bikes all hate it. I shop for alcohol free gas or at least real low alcohol content. My KLR will quit running, act like it has water in the gas, won't idle, cut out at road speeds. Kill and until I drain the bowl and start fresh, won't start. If draining the bowl clears up the issue and it repeats itself, you may have a bad load of gas. Gas and water will separate. Usually in the float bowl.
I'm going to start by draining the carb float bowl into a transparent glass container and seeing if the gas appears to be contaminated.

Adjusting the idle speed screw on the carb would obviously be the quickest and easiest thing to try, but even if doing that stopped the bike from dying every time I let off the throttle, might I not just be putting a band-aid on the problem? I mean, if there *is* something gumming up the fuel flow somewhere, wouldn't messing with the idle screw just be compensating for the real problem rather than addressing it at the root? Feel free to tell me if my reasoning is bad; I'm no mechanic.

I've removed the seat and fuel tank and am now trying to remove the carb. The Clymer manual instructs me to "remove the clamps from the air filter housing duct and intake duct," but I can't see how to do so. I'm looking at chapter 8, The Fuel System, in the section called Removal and Installation, if anyone would be so kind as to crack open his copy and give me a hand. Thanks.
 

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You don't have to remove the carb to drain the float bowl. Cabron--a drain screw and dump tube make the job easy.

Also, no need to remove the carb to access the fuel screw; loosen the hose clamps and roatate the carb so you can remove the anti-tamper plug and adjust that sucker--use a small flat-bladed screwdriver, 1.75 out is where I'd start from.

If you're intending to perform a complete carb disassembly, cleaning, and adjustment, of course you must remove the carb. However, you can get a lot of cleaning done by dropping the float bowl, and aerosol-spraying some carb cleaner into all the jet orifices (WEAR EYE PROTECTION).

Since you report problems only at idle, and don't want to adjust the idle speed screw for fear of masking another problem, I'd say you're limited to the fuel screw (previously discussed, accessible from the bottom of the carb, engine side), and the pilot circuit. It's really easy to get the pilot jet stopped up; you can remove it, inspect and clean it with a small flat-bladed screwdriver from the mounted carb, with the float bowl removed.

All that said, the carb's eaiser to service when removed, surely; however--you don't HAVE to remove the carb to perform considerable maintenance on the component.

While you're fooling around with the carb, I'd consider the fuel screw adjustment mandatory; might as well shim the carb needle (one # 4 washer, the "22-cent mod") and drill the slide vacuum port to 7/64" diameter while you're at it. You can tilt the carb as mentioned to remove the mixing chamber cover (black plastic thingy held on with four machine screws) and pull the slide an diaphragm.

When you rotate the carburetor, mind the "choke" (enricher). It's plastic cap is rather fragile. "Don't try this at home," but . . . some of the big boys on the playground say they've rotated their carbs sufficiently to work on 'em WITHOUT removing the "choke." The thing's something of a bear to unscrew or to thread in tight places; 12 mm hex flats, if that's any help (you've gotta peel back the rubber cover to reach the hex).

Here's a primer on the CVK40, if interested:

http://www.gadgetjq.com/keihin_carb.htm

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I looked at Clymer's carb removal instructions; seem reasonably valid to me.

Removing the carburetor from its "ducts," aka rubber hoses, may take some force and exploitation of the hoses' elasticity after loosening front and read hose clamps. Silicone lubricant, I find, is sometimes useful in encouraging the carb's metal circumferences to enter or to depart those "ducts."

Good luck; I appreciate your industry and your initiative in performing your own maintenance.
 

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Discussion Starter #13
You don't have to remove the carb to drain the float bowl. Cabron--a drain screw and dump tube make the job easy.

Also, no need to remove the carb to access the fuel screw; loosen the hose clamps and roatate the carb so you can remove the anti-tamper plug and adjust that sucker--use a small flat-bladed screwdriver, 1.75 out is where I'd start from.

If you're intending to perform a complete carb disassembly, cleaning, and adjustment, of course you must remove the carb. However, you can get a lot of cleaning done by dropping the float bowl, and aerosol-spraying some carb cleaner into all the jet orifices (WEAR EYE PROTECTION).

Since you report problems only at idle, and don't want to adjust the idle speed screw for fear of masking another problem, I'd say you're limited to the fuel screw (previously discussed, accessible from the bottom of the carb, engine side), and the pilot circuit. It's really easy to get the pilot jet stopped up; you can remove it, inspect and clean it with a small flat-bladed screwdriver from the mounted carb, with the float bowl removed.

All that said, the carb's eaiser to service when removed, surely; however--you don't HAVE to remove the carb to perform considerable maintenance on the component.

While you're fooling around with the carb, I'd consider the fuel screw adjustment mandatory; might as well shim the carb needle (one # 4 washer, the "22-cent mod") and drill the slide vacuum port to 7/64" diameter while you're at it. You can tilt the carb as mentioned to remove the mixing chamber cover (black plastic thingy held on with four machine screws) and pull the slide an diaphragm.

When you rotate the carburetor, mind the "choke" (enricher). It's plastic cap is rather fragile. "Don't try this at home," but . . . some of the big boys on the playground say they've rotated their carbs sufficiently to work on 'em WITHOUT removing the "choke." The thing's something of a bear to unscrew or to thread in tight places; 12 mm hex flats, if that's any help (you've gotta peel back the rubber cover to reach the hex).

Here's a primer on the CVK40, if interested:

http://www.gadgetjq.com/keihin_carb.htm

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I looked at Clymer's carb removal instructions; seem reasonably valid to me.

Removing the carburetor from its "ducts," aka rubber hoses, may take some force and exploitation of the hoses' elasticity after loosening front and read hose clamps. Silicone lubricant, I find, is sometimes useful in encouraging the carb's metal circumferences to enter or to depart those "ducts."

Good luck; I appreciate your industry and your initiative in performing your own maintenance.
You weren't kidding when you said it might take some force to get the carb free of the front and rear ducts. I used a lubricant, and it was still a bitch.

I'm glad you mentioned the plastic hex screw connecting the choke to the carb; it's the last thing I need to loosen to free the carb from the bike. It looks like it's going to be even more of a PITA than getting the carb free of the ducts, but I'm going to go ahead and detach it so that I don't have to mess with the carb in the freezing outdoors.

Thanks. I'll keep you posted.
 

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I'm going to start by draining the carb float bowl into a transparent glass container and seeing if the gas appears to be contaminated.

Adjusting the idle speed screw on the carb would obviously be the quickest and easiest thing to try, but even if doing that stopped the bike from dying every time I let off the throttle, might I not just be putting a band-aid on the problem? I mean, if there *is* something gumming up the fuel flow somewhere, wouldn't messing with the idle screw just be compensating for the real problem rather than addressing it at the root? Feel free to tell me if my reasoning is bad; I'm no mechanic...

The idle has to be at least 1100-1200 or the bike will die. It's just a screw that adjusts the throttle stop. Try the simple fix first, it's not a band-aid it's an adjustment to the idle circuit on the carb.

Does the bike run good except for when you get near idle? Starts up OK? Throttle response good? A fuel delivery problem would be more evident as the throttle is opened up. The motor is using the least amount of gas at idle so even if it was getting a reduced flow it will idle.
 

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Discussion Starter #15
Removing the choke cable from the carb turned out to be more of a pain than I wanted to deal with, so I just drained the float bowl into a clear glass container with the carb still attached to the bike. I took some pictures of the gas in the container with my cell phone, but they're too blurry to show you much of anything, so I won't bother posting them. If there's water in the gas, or some other kind of liquid contaminant, should it be pretty obvious? The fluid I've got here looks very homogeneous throughout, with no apparent separation at all. But I do have what appears to be a small amount of sediment--small white particles--sitting in the bottom of the glass. (And yes, they definitely came out of the carb; I made sure there was nothing in the glass before I drained the float bowl.) Is it normal to have some of this?

Spec, to answer your questions: I wouldn't say it runs well when I get it past idle. It's definitely rough, but as long as I keep the RPMs up by always applying the throttle, it won't die. If I close the throttle, at any speed and in any gear, the engine dies as soon as the RPMs are allowed to drop low enough. If I've been riding at, say, 4k RPM and I close the throttle, I can keep the engine going by reopening the throttle before the RPMs drop past the point of no return.

It does start fairly easily, but I have to give it some gas while I hit the ignition button, and it will immediately die if I close the throttle. Hope that helps.
 

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I'm with Spec; the idle speed adjustment might have cured everything.

Failing that:

From the symptoms, sounds like occluded PILOT (IDLE) CIRCUIT, probably clogged pilot jet; and/or--fuel screw set too lean.

The choke plunger cap is not difficult to remove, if you can obtain access to it. The plastic cap is fastened to the carburetor body by tapered threads on the cap. You only peel back the elastic coating, and affix a 12-mm open-end wrench (or pliers) to the hex flats on the cap to loosen it, then unscrew with fingers. The cap, cable end, and plunger all come freely out of the carb when the cap is uncrewed.

If the bike ran at all, I doubt moisture in the float bowl is the problem; water in the float bowl is most noticeable at mid- and high-speed operation, NOT at idle, because--the needle jet (dominating air/fuel mixture at mid-throttle) and the main jet (dominating air/fuel mixture at wide-open throttle) are lower in the float bowl than the pilot jet (dominating idle air/fuel mixture). Thus, since water is heavier than gasoline, the needle and the main jets are affected before the pilot jet; and, as mentioned, the pilot jet (highest elevtion of all jets) dominate idle mixture.

Sometimes, with water in the fuel bowl, a bike will idle fine, but stall when the throttle is opened and water inters the fule mixture as the needle and main jets are uncovered.
 

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I beleave your really over thinking this problem folks. It's not that the replys are not any good, I just think the problem is an easy one.

When the weather gets real cold he motor fattens up, warmer it leans out.
I would lean the pilot circut out a bit and turn the idle screw up a bit till it idles. The motor is just reacting to the temp out side it's running in.
As you moveinto warmer weather the bike will start to run better or as good as it did.
If your riding in the winter most folks will go to a thiner oil, and in the summer you go a little thicker. Carb adjusts are the same way, you have to do minor adjustments do to the changes of the season.

Kurt
 

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Removing the choke cable from the carb turned out to be more of a pain than I wanted to deal with, so I just drained the float bowl into a clear glass container with the carb still attached to the bike. I took some pictures of the gas in the container with my cell phone, but they're too blurry to show you much of anything, so I won't bother posting them. If there's water in the gas, or some other kind of liquid contaminant, should it be pretty obvious? The fluid I've got here looks very homogeneous throughout, with no apparent separation at all. But I do have what appears to be a small amount of sediment--small white particles--sitting in the bottom of the glass. (And yes, they definitely came out of the carb; I made sure there was nothing in the glass before I drained the float bowl.) Is it normal to have some of this?

Spec, to answer your questions: I wouldn't say it runs well when I get it past idle. It's definitely rough, but as long as I keep the RPMs up by always applying the throttle, it won't die. If I close the throttle, at any speed and in any gear, the engine dies as soon as the RPMs are allowed to drop low enough. If I've been riding at, say, 4k RPM and I close the throttle, I can keep the engine going by reopening the throttle before the RPMs drop past the point of no return.

It does start fairly easily, but I have to give it some gas while I hit the ignition button, and it will immediately die if I close the throttle. Hope that helps.


More info, good...

Carbs have jetting circuits that relate to the throttle position not the rpm of the motor. Here's a page with a good explantion: Motorcycle Carburetor Theory 101

I'm with Damocles... sounds like the pilot jet is plugged up. Take all the jets out and blow them out with carb cleaner or brake cleaner. Be sure that the little holes on the sides of the jets are clean. Clean out all the passages also.

While you have the bike apart check the valves. When they get tight the bike will get hard to start and not have the power it once had.
 

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When the weather gets real cold he motor fattens up, warmer it leans out.
I would lean the pilot circut out a bit and turn the idle screw up a bit till it idles. The motor is just reacting to the temp out side it's running in.
Resecting your opinion, Kurt, seems to me one wants an engine fuel-richer in cold weather. After all, the "starting enricher" (choke) is used when the engine is cold.

Other factors may be at play. Regardless, a fuel screw backed out 1.75 turns works year-round on my KLR650.

Back to Cabron's situation; while a stopped-up pilot circuit is suspected, I'd rejoice alongside him if a fuel screw adjustment cures his problem, whether turning it fuel-richer or -leaner.
 

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Resecting your opinion, Kurt, seems to me one wants an engine fuel-richer in cold weather. After all, the "starting enricher" (choke) is used when the engine is cold.

Other factors may be at play. Regardless, a fuel screw backed out 1.75 turns works year-round on my KLR650.

Back to Cabron's situation; while a stopped-up pilot circuit is suspected, I'd rejoice alongside him if a fuel screw adjustment cures his problem, whether turning it fuel-richer or -leaner.
Agreed, you do need the choke to start the bike. But when you turn it off and the bike runs on the pilot it could run fat because of the cool weather OR air. When the air enters the cab it atomizes the fuel for a better burn and fuel air mix. When the air is real cold the fuel does not atomize as well when it's warmer. So if you lean down the pilot just a tad (1/4 turn at a time) it will lean it just enough to burn a little cleaner.
I'm like you also. I run at 1 3/4 turns myself. I just turn the idle srew up in the winter when needed.

But then again he could be having a problem that we can only guess at with out hearing it run.

Kurt
 
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