2000 KLR650 Low RPM Bog and Cold Idle Issues | GTAMotorcycle.com

2000 KLR650 Low RPM Bog and Cold Idle Issues

MaksTO

Well-known member
Hey all!

I've posted this in other places before but just have not gotten anywhere with this. Seems to come up as a 2-stroke problem every time I google lol.

My bike (2000 KLR650) has 50,400km, FMF Q4 Full system, and MCP Carb Kit. Worked perfectly last year.

The issue:
This year since pulling it out in March or so, I've noticed a low RPM bog. When cold it happens around 1,500rpm when slowly applying throttle. It will bog down a few hundred rpm, and then shoot up and be fine. Sometimes stalls like this when cold (happened to me mid way through a left turn and almost got hit... very scary...). Idle is a bit shaky at around 1,000-1,100rpm when cold, Idles fine at around 1,300-1,500rpm when hot.

Once warmed up the bog happens around 2,500rpm, and stalling is no longer an issue. Just a noticeable hiccup in the power delivery.

The worrying thing is when its cold (I warm it up for about 60 seconds, and that's not even enough anymore... never had this problem when it was cold last year) it will sometimes make a "knock" or "stutter". Only once. It feels like the engine stops combusting (a misfire?), and it just forces its way inertially through a cycle before firing up again. Sometimes it will stall out pretty aggressively, sometime it will just lightly hiccup and make a weird noise. This ONLY happens when the bike is cold - 1-5 minutes from starting. Again, used to take 30-60 seconds with choke on before I could ride it totally fine... This is a new issue and its kind of freaky...

What I have done:
1) Seafoam, didn't work
2) Spark Plug, no change
3) Total carb tear-down... 3 times. Once with an ultrasonic cleaner, and all of the rebuild attempts used up about a half can of carb cleaner through all of the ports... I have a very very hard time believing something is plugged in the carb. Needle, pilot jet, and float bowl gasket are all new as of late last summer. I hear that the needle jet in the front of the carb wears out? Though this shouldn't cause a low rpm bog... I know my enricher circuit U-ring is quite grimy, but that should only affect deceleration (pops etc, whatever). Float height looks fine, I never messed with it.
4) Confirmed exhaust manifold torque - It's good.
5) checked for air leaks in the carb boots. It seems fine when spraying combustibles all over it, though I still ordered replacement ducting to make removing this stupid carb easier.
6) Fresh Rotella T4 and oil filter, no change.

What I need to do, but not sure if it can be responsible for this issue:
1) Valve Clearance (way overdue... need to wait until I have space to do it as shop rates are way too insane...). No hot start issues, so not even sure if this needs to be urgently addressed...
2) Open left side - I'm sure doo has been done at some point with this high mileage, but it stresses me out not having seen it in person.
3) Open right side? Could plugged oil screen cause engine hiccups? I imagine if this was the case the bike would've died by now. Again, runs great in mid-upper rpm ranges, and I've been daily driving since March basically with no changes. Hesitant to open right side because I don't want to rebuild the water pump, and I hear the shaft shears easily and requires a full engine tear-down to fix. F*** that...


Would LOVE anyone's input on this... It's driving me absolutely mad, and is kind of ruining my joy of riding at this point... Taking it to a shop is not really financially an option right now, and I don't really have a consistent work space so I can only very sporadically tackle these issues one at a time.
 
Not super familiar with KLR 650, it looks like there was multiple versions of the petcock. Does your have a PRI (prime) position? If so, does riding with it in that position make any difference?
 
Not super familiar with KLR 650, it looks like there was multiple versions of the petcock. Does your have a PRI (prime) position? If so, does riding with it in that position make any difference?
KLR has a vacuum diaphragm operated petcock. I have a manual one on hand, but have not installed yet. From what I understand, petcock diaphragm issues on the KLR become apparent at high rpm, rather than low - unless maybe something super weird and irregular happened to it. Regardless, it is actually a part I am going to change the next time my tank is low!

Edit: to answer your question directly. No prime. Mine has "on", "off", and "res"
 
Long shot but easy to check, open lid on gas tank and see if it is under suction (I was thinking that if you ride it when it's warm and then park it where it's cool, if tank wasn't venting properly, resulting in vacuum in tank could wreak havoc on mixture).
 
Seeing as how this problem developed after the bike sat for the winter, my bet is on a clogged passage in the carb. In your description of the carb overhaul you mention using carb cleaner. The only way to properly rebuild a carb is to soak it overnight in a proper cleaner. Yamaha sells a Yamalube one that you mix with water and it works well. No amount of spraying will clean out a passage that is blocked with gummed up fuel.
 
1 dump your overwinter fuel, refresh with good quality stuff.

2 give your ignition circuit (coil, plug wire and boot) a good spray down with WD40 to eliminate moisture

3 Try running with choke on part way, if this clears the low end bog you need to clean your carb. When you clean a carb, chase passages with fine wire and use compressed air to blow them out.
 
it beats the alternative

1 dump your overwinter fuel, refresh with good quality stuff.

2 give your ignition circuit (coil, plug wire and boot) a good spray down with WD40 to eliminate moisture

3 Try running with choke on part way, if this clears the low end bog you need to clean your carb. When you clean a carb, chase passages with fine wire and use compressed air to blow them out.
We're always told to NEVER use wire to clean carb passages. That said I use wire guitar strings. I think an E string is the right size.
I also agree with Mike about trying the choke. That should be a good indicator.
 
We're always told to NEVER use wire to clean carb passages. That said I use wire guitar strings. I think an E string is the right size.
I also agree with Mike about trying the choke. That should be a good indicator.
Wire (or a drill) through jets is a bad idea. Through passages shouldnt be a big deal.
 
Sorry, MIA for a bit. Will address these individually:

@GreyGhost I've tried starting cold with tank lid open. No difference. Forgot to mention this attempt in my original post.

@ToSlow I personally did not change it. I got this bike with 47,000km on it, and I think it has been done from what I remember. Given the first gen issues with it I'd be shocked if it survived this long with a broken doo. I want to open it up sometime to double check for my sanity, but I just don't have the space to do it right now :/

@bull958 I might try that when I have the carb out again. Plan is to borrow a friends carb off their KLR and test it out to see if there is any difference in the bogging. Maybe an overnight soak will do it while I'm trying a different carburetor...

@Mad Mike
1) I have gone through about three so far since winter, one of which had seafoam in it. Should be clear now with out totally dumping no?
2) Will try to take a look at ignition circuit to see if that might be a problem. I did read somewhere that some electrical issues can very closely mimic carburetion problems.
3) I've heard air compressor is the way.. I'm hesitant to use wire :$ Long soak and air comp will hopefully do it... Just need to locate an air compressor...
4) Regarding choke, I think the bog goes away with the choke on - I will have to test that out again. Though the choke has very little effect on my bike unless its halfway out when starting cold.

Thanks all for the suggestions! Will have to find time to test these things out... I'm not very electrically inclined so locating and cleaning the starter circuit might be a challenge but I'll see.
 
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I'm just going to assume that you have checked the airbox for mice nests or other blockages?
If the valves are long overdue it can cause stalling as well as long warmups, not just hard hot starts.


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4) Regarding choke, I think the bog goes away with the choke on
That would suggest you have a pilot/idle circuit problem.
CVK carb? Typical. REPLACE the pilot jet, then adjust the idle circuit

... you can "clean" a jet with a drill, wire, guitar string... what ever ... BUT you don't know if you got it 100% clean.
Jets are a metering device, a VERY precise metering devise. Getting a pilot jet 98% clean is the same as dropping a jet size.
Scratching the crap out of jet with a hard metal THING also effects flow.

Jets are cheap... but those incredibly CHEAP jets on amazon are knock offs and are JUNK.
In Canada; Winner's Circle is the distributor for Mikuni and Keihin jets and carb parts. (It's probably faster to order them direct from Sudco)
 
I'm just going to assume that you have checked the airbox for mice nests or other blockages?
If the valves are long overdue it can cause stalling as well as long warmups, not just hard hot starts.


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Airbox looks good. I tested it when putting in a new filter early thig season. Tried it with filter in, filter out, side door open, etc. Doesn't seem to be an air box problem.

Good to know valves can cause long warmups. Need to figure out a space to do the job and take care of that soon hopefully.
 
That would suggest you have a pilot/idle circuit problem.
CVK carb? Typical. REPLACE the pilot jet, then adjust the idle circuit

... you can "clean" a jet with a drill, wire, guitar string... what ever ... BUT you don't know if you got it 100% clean.
Jets are a metering device, a VERY precise metering devise. Getting a pilot jet 98% clean is the same as dropping a jet size.
Scratching the crap out of jet with a hard metal THING also effects flow.

Jets are cheap... but those incredibly CHEAP jets on amazon are knock offs and are JUNK.
In Canada; Winner's Circle is the distributor for Mikuni and Keihin jets and carb parts. (It's probably faster to order them direct from Sudco)
Idle circuit may be an issue. When I had it disassembled I know the U-Ring or O-ring on the idle enricher circuit was starting to come apart - maybe that's causing problems. Thinking that may be the problem. Might replace it and see what happens. All the diaphragms seem good on the idle circuit and the slide though.
 
Just a quick update!

1) Bike is not doing the stalling thing anymore - though that might be because it's warmer outside and the engine doesn't get stone cold these days.

2) I replaced the pilot jet, which might've done something, might've not. Still does the low rpm bog slightly. Definitely a dead spot somewhere in the 1.5-2.5k range. Took it on an off road trip last weekend and it didn't cause me any problems despite being in first and riding the clutch and gunning the gas a bunch, so it's not bothering me too much as long as bike continues to NOT stall.

3) Replaced idle enricher U-ring, which helped the exhaust popping slightly. The aftermarket idle enricher diaphragm was GARBAGE. The plunger on it was about 1-2mm thicker than on the OEM one, so it would never actually open fully when you kill the throttle, making it pop like a machinegun... so embarrasing to test ride that one... I just put the stock idle enricher diaphragm on, but left the new U-ring in there.



NOW, some questions regarding valves:

I don't have the space to do it at home, but a friend in Brampton offered to let me do it in his garage. Clymer manual states to measure when cold (obviously), and internet forums say they leave vehicles overnight to cool before measuring and that doing anything else is asinine. Would I be safe to drive the bike there (45 min drive), let it sit for 3-4 hours or until cold to the touch, and then measure clearances? Has anyone done anything similar before? It's probably not ideal, but it's either doing that, or taking it to a shop and bleeding my wallet dry...
 

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