'07 KLR 650 stuttering or worse at 4-5k RPM when warm

There are of course, lots of similar threads all over the Internet about similar sounding fueling problems, but I still want to air my particular issue here since there's a bunch of smart guys here and I need help thinking this through since the bike is new to me and I haven't ridden in a VERY long time. SUPER excited getting back on a bike though, other than this little hiccup in my first week of ownership.

Description of problem

No problem until sometime after the bike comes up to operating temp...
Starts by missing slightly but develops into a very disconcerting stutter/surge under slight deceleration or slightly high RPM cruising (starts around 4k keeps doing it until 5+K (more or less)
I can mitigate the problem when it starts to get bad by "pumping" the throttle or put another way, by multiple quick little increases in throttle. By doing that, I can keep riding. If I don't do that, the problem gets bad enough that I need to stop riding for a little while, which sort of resets the clock on the symptoms.
The first time it happened I though I was out of gas. I switched to reserve and found a gas station right away. Thought it was weird that it only took 4 gallons since it holds 6.x
Since that time, I tried switching to reserve during the stuttering and surging but it didn't help. I had wondered if there was a restriction in the petcock that would clear in the reserve position.

What I've done so far and what I'm thinking
Replaced the spark plug. It was a little white looking... no real difference.

Put in the recommended dose of SeaFoam... at first, (10 minutes of riding) I started to think SeaFoam had worked a miracle but eventually I started to see the problem again. Seemed less severe but I think its more because the throttle fiddling I described above helps keep me going. I've considered that giving the fuel treatment more time might help, or adding more than the recommended amount...

Even though the vacuum line to the petcock seems/looks good to me, I wonder if when the engine gets warm, the line collapses. This would explain why the problem manifests only with a warm engine.

I've only had an opportunity to run with the SeaFoam a couple days for 45 minutes or so each time.

Seems like a fuel delivery problem (as opposed to electrical) since I can sort of fix it by fiddling with the throttle.

At the moment, I'm interested in keeping a vacuum operated petcock, so I would rebuild or replace with a factory one if it turns out to be the cause. I get why people like the gravity fed solution but I kind of like not having to turn the fuel off. I also kind of like the kickstand safety switch, when it's working like it's supposed to.

Or, is it a carb problem...

Once I'm sure SeaFoam isn't going to work a miracle for me, I'll have to make a decision where to start first.

Thanks much for anyone's thoughts on this..

Gas cap vent clogged? Try riding with the cap loose or just tape it in place. Also when it starts happening again, open the cap.

Is the bike completely stock, or are some things changed?

This is way out there, but it happened to me. My '00 KLR ran perfect around town, using half throttle up to 4,000 rpm. At highway speed it would only rev to 4500 and had very little power, top speed of 65 or so. Long story short, it ended up being a loose baffle in the muffler. Apparently it blocked enough flow to prevent full power, but not so much that it wouldn't run at low speed. Sometimes it seemed to fix itself if I backed off the throttle, I suppose that moved the baffle to a different spot.

Bang on the muffler, and if you hear anything rattling, remove or replace it and see what happens.

endoman said:

Gas cap vent clogged? Try riding with the cap loose or just tape it in place. Also when it starts happening again, open the cap.

Is the bike completely stock, or are some things changed?

Click to expand...

Oops, forgot that I also opened the cap at one point which didn't help. Thought for sure that was going to be the problem 8-(
The bike is stock as far as engine and carb and exhaust and air box.

AndyT said:

This is way out there, but it happened to me. My '00 KLR ran perfect around town, using half throttle up to 4,000 rpm. At highway speed it would only rev to 4500 and had very little power, top speed of 65 or so. Long story short, it ended up being a loose baffle in the muffler. Apparently it blocked enough flow to prevent full power, but not so much that it wouldn't run at low speed. Sometimes it seemed to fix itself if I backed off the throttle, I suppose that moved the baffle to a different spot.

Bang on the muffler, and if you hear anything rattling, remove or replace it and see what happens.

Click to expand...

There's why I bothered posting! I knew folks would have good ideas that I wouldn't have come up with in a reasonable amount of time on my own. I will give the muffler a bang or two and see what that reveals... (tomorrow)

I got a dollar that it is the vacuum line for the petcock. The same thing happened to Calgary Yogi and I remember him telling me it was the most frustrating thing to try and track down. His symptoms were identical to yours.

AndyT said:

This is way out there, but it happened to me. My '00 KLR ran perfect around town, using half throttle up to 4,000 rpm. At highway speed it would only rev to 4500 and had very little power, top speed of 65 or so. Long story short, it ended up being a loose baffle in the muffler. Apparently it blocked enough flow to prevent full power, but not so much that it wouldn't run at low speed. Sometimes it seemed to fix itself if I backed off the throttle, I suppose that moved the baffle to a different spot.

Bang on the muffler, and if you hear anything rattling, remove or replace it and see what happens.

Click to expand...

Well, I thought it would be the fuel line, but you aren't the first person that I have heard that has had this problem too. Okay, so I'll change my bet.... It will either be the fuel line of the muffler baffle.

I am VERY happy to report that the problem has been solved!

So far, KLRs kind of make sense. Based on the symptoms and what little I understood thus far, and of course information from those that have gone before me, I replaced the vacuum hose that goes from the carb to the petcock. Took a nice ride of sufficient length with no stuttering whatsoever.

I stopped by an auto parts store on the way home. They didn't have what I thought I wanted so I got what they did have. It was some "Hard" chemical and heat resistant tubing. I used two cut pieces of the original hose as fittings for the ends of the new hard tubing, and wire ties to snug up the connections. It's probably hard to make out anything from the photo but, for what it's worth...

And so, apparently the vacuum line was indeed collapsing under certain vacuum conditions when it got hot enough, causing a loss of vacuum to the petcock which then cut off the fuel supply.

Thank you DFW_Warrior, AndyT, and endoman for taking the time to step up and offer some assistance

Heck yeah! Glad she is up and running again.

White looking spark plug? Sounds like a lean condition. If it got better when you replaced the vacuum line to the petcock, I'm guessing that you had a vacuum leak.
Glad it's wotking!

rt

definitely had a vacuum leak. they run very lean at part throttle cruise. vacuum leak made it bad enough to misfire. also it might be rich on the idle circuit, since you didn't notice any driveability issues down low.

Glad you found the problem, I was going to suggest the line from the carburetor that hangs down below the bike, or the line that you do the T mod to, is this the same line as the vacuum line or another one. I did have that line plug up and the bike ran somewhat the same way.

John

For the benefit of anyone reading this because they have a similar problem with their KLR, I wanted to add that although the last thing I did (replacing the vacuum hose to the petcock) seemed to take care of the problem once and for all, I eventually started to see the same symptoms AGAIN!
A few months back when the symptoms returned, I drained the carb float bowl and found about 10 tiny black specks in the fuel. I rode the bike awhile, the symptoms returned, I drained the carb, more tiny black bits. So I installed a inline fuel filter from Eagle Mike. Haven't had that problem for a few months now.
So maybe the petcock is breaking down and introducing those tiny black bits? If so, I guess I should replace or rebuild the petcock, but for now, it seems the filter is catching the bad stuff and it's been running great... well, maybe I'll submit a new post about how hot the engine gets in traffic when it's hot outside ...

Make sure the fan is fanning. If you haven't relocated the fuse, it'll be under the tank. Lot of folks zip tie it up over the coolant tank for easier access. When the fan isn't doing it's thing...klr's get pretty warm. And then there is also the coolant/fan switch....

_RG_ said:

Make sure the fan is fanning. If you haven't relocated the fuse, it'll be under the tank. Lot of folks zip tie it up over the coolant tank for easier access. When the fan isn't doing it's thing...klr's get pretty warm. And then there is also the coolant/fan switch....

Click to expand...

Now that everything else is smooth, and it's getting hot outside, I need to start looking more closely at the temp situation.
All I can say before looking more closely, is that I hear the fan switch on for 30 seconds or so almost every time I shut the bike off, but I've not checked to see if it comes on while I'm riding when the guage is at 3/4 r so. I peeked under the radiator cap once and saw coolant at the top. The overflow tank is at the low level indication when the bike is cold... Also, when it gets real hot, or what I perceive as hot, sometimes the bike starts to act like it's vapor locking, that fuel starved, stuttering kind of behavior.

The Thermo Bob mod that Dahveed had done on his 09 KLR kept the temp guage needle generally in the middle of the range without a lot of movement at different speeds (engine or bike) Beside the well known DooHicky mod...I'd say the Thermo Bob cooling mod was prob the best thing for that bike.

& then there's the more costly big bore kits....next in line of useful engine mods.

The hotter an engine gets, the leaner it runs. The leaner and engine runs, the hotter it runs. I'm guessing that you haven't rejetted the carbs. They come very lean from the factory, so if the engine gets really hot it will also get really lean. You may feel "surging" at a steady throttle or even feel the like the fuel gets cut off for a second when you grab a handful of throttle.

You might want to explore rejetting. You'll get more power and your bike will run cooler. I doubt you'll lose much mileage. You might even gain some if it's as bad as you say.

Moekazi said:

The hotter an engine gets, the leaner it runs. The leaner and engine runs, the hotter it runs. I'm guessing that you haven't rejetted the carbs. They come very lean from the factory, so if the engine gets really hot it will also get really lean. You may feel "surging" at a steady throttle or even feel the like the fuel gets cut off for a second when you grab a handful of throttle.

You might want to explore rejetting. You'll get more power and your bike will run cooler. I doubt you'll lose much mileage. You might even gain some if it's as bad as you say.

Click to expand...

Seems like a great idea. I read up on that and then somewhere along the line forgot about it. I'd like to do the Thermo-Bob mod/upgrade too (thank you Mr2mch), and I think I will, but I could probably re-jet the carb right now without getting in trouble with my wife

Thank you Moekazi

I'll post again here after I do the work... hopefully getting the carb out isn't too big of a deal...

In the interest of providing helpful information for others that might experience the problems I described earlier in this thread, I'm posting an update here...
Months after the last "fix", I started having the problem again, so I figured out a way to bypass the vacuum function of the stock petcock. and then went out on a ride this afternoon. Seems as though bypassing the vacuum operated petcock solved the problem. No more popping on deceleration, and no more stuttering/choking/starving for fuel randomly while on the freeway or cruising at 4K+ rmp at whatever speed.
I suspect that every time I had this problem in the past, it was probably the petcock going bad, and/or related to the petcock. I added some SeaFoam and it got better one time. I replaced the vacuum hose and it got better one time. I cleaned little black bits out of the float bowl and added a EM fuel filter and it got better one time. Now that I finally bypassed the darn stock petcock and it got better again, I guess I shouldn't have any great confidence that it is THE cause, but if the problem doesn't resurface within a couple months, I'll be thinking it's been that vacuum operated petcock all along and I'm gonna become a huge manual petcock fanboy!

I know on a friends bike and mine also we had a fuel line breaking down and may be due to corn in our fuel? We both had black stuff in our carbs and it turned out to be the fuel line causing it. Replaced and no more black stuff going into the pilot jet. We had both installed filters but ended up having to replace the fuel line.

... mmmm, fuel line... Hadn't thought about that piece of the fuel delivery system, as far a bits go. Seems like there are many reasons for having a filter. AND, one of these cold unrideable weekends I might wanna replace my aging fuel line too.


Sent from my iPhone using Tapatalk

I just replaced the brittle leaking line on my 07 Klx250 yesterday. First service work I've done on a motorcycle since injury in April and it was painful messing with it. One of my fuel lines was leaking at a tank connection. Definitely not something you want to fail while you're flying your bike over the Atlantic Ocean ...

kojack06 said:

I just replaced the brittle leaking line on my 07 Klx250 yesterday. First service work I've done on a motorcycle since injury in April and it was painful messing with it. One of my fuel lines was leaking at a tank connection. Definitely not something you want to fail while you're flying your bike over the Atlantic Ocean ...

Click to expand...

Maybe I need to stop feeling like my bike is still kinda new. 07 was awhile ago now I reckon.


Sent from my iPhone using Tapatalk

Ours are 2006 models purchased at the same time and same dealer. First fuel line replacement was on my buddies bike 2 years ago and mine lasted 1 year longer. Mine had over twice the miles than his did last year. His sat up more than mine but don't know if that had anything to do with his failing before mine? It was a pain in the butt for him when the black stuff started showing up before he replaced the fuel line. Took his carb off about 10 times and clean to get to run right again.
When it showed up in mine causing it to run bad I knew what to do right away.

Crud... in spite of the now bypassed vacuum portion of the stock petcock, today when I was riding and it was a little warmer, the symptom returned. So, probably not petcock related. Feels like all of a sudden there is intermittently no spark. I've also described it in the past as feeling like it's starving for fuel but... now that I can see the fuel through the filter, it seem like that's not it. I see at least a little bit of fuel flow when it's misfiring at 4 or 5K rpm. And it's always fine again if I let the bike sit for a bit.
Guess there could still be something going on with the carb? One consistent thing is that operating temps are always on the hotter side when it happens. Just slightly over the middle on the temp gauge.
CDI? Coil?
Sheesh...

Was it windy where you are at, and was it a cross wind?
I ask because the CVK keihn carb found on your bike is particularly sensitive to pressure variations on the vent. It has to be routed precisely to the exact spot the factory put it at.


Sent from my iPhone using Tapatalk - now Free