KLR You Experienced? I am now...

Re: KLR You Experienced? Err, kinda not really.

Nice ride! Not unusual for big bore kits to run rich. Try going down 1 size on the main jet. I find it is best to change one thing at a time when tuning carbs.

Re: KLR You Experienced? Not really.

Thanks man and good advice - I'll definitely do that. One thing at a time - absolutely.

Looking back on this thread there's a lot of info on carbs - how they work and how to tune them. This is really helpful -

"If you think about the basic function of the carb:
The piston goes down and causes an air void that atmospheric pressure feels the need to fill. The air flows through the carb at high speed and runs over the jets, this vacuum effect sucks fuel up the jets into the air stream (and then into the cylinder). Stock you're getting a certain amount of air flow through that carb orifice.
When you go up in bore that "void" gets bigger so you need more air to fill it. The only way to get more air through that same carb in the same timeframe is to pull it in faster, which increases the velocity over the jets and sucks more fuel in. So on the same carb settings with a bigger bore you get more fuel than you did with the stock bore.

It's not always linear because it all depends on the design of the carb, size of the jets, etc etc but in general that's how it works.

Now that it's running close to right you can do some plug chops to see if that fixed the issue or not, you could still be rich or lean with the stock jets and you'll likely need to fiddle a bit to get it right".

Thanks for that Sonic - that gave me a much better understanding of how the carb actually functions.

The spark plug still looks like this -



Irk suggested that this could be because the choke is stuck open. I know I pulled the carb and checked the choke (enricher) but as far as I can tell it's working fine. I rarely need the choke however.

I've got stock jets in the carb - I'm going to do what's been suggested and try a smaller jet size - it seems like the biggest problem at the moment is at WOT and it's my understanding that the main jet governs this part of the throttle position.

Could someone remind me what the needle is responsible for? The stock needle is not adjustable, but the Dynojet needle (which I have, but not installed) has various clip positions.

Re: KLR You Experienced? Not really.

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Re: KLR You Experienced? Not really.

Was that a flat out run and plug chop, or just riding around to get back to the shop?

Not needing choke is a sure sign that the bottom end is too rich. Fit a NEW OEM type pilot jet and try again. Also inspect the enriching system. Sometimes the "seat" is damaged and allows extra fuel in and often the choke plunger is hard and fails to seal.

Get idle and just off idle right first.

Re: KLR You Experienced? Not really.

you have a pumper carb on the bike and if you state it starts with out the choke then you have a problem that is not just jetting i would guess

they always need the choke cold

they are normally lean as hell and need the pump to get them into range im wondering if you have a issue that s letting it bypass through the pump

like the pump rod clearance is not right so its spraying to much to often?

or the float is high and its getting to much fuel

i would verify all of it before you do a bunch of jetting and find out that is not the issue

Re: KLR You Experienced? Not really.

cxman said:

you have a pumper carb on the bike and if you state it starts with out the choke then you have a problem that is not just jetting i would guess

they always need the choke cold

they are normally lean as hell and need the pump to get them into range im wondering if you have a issue that s letting it bypass through the pump

like the pump rod clearance is not right so its spraying to much to often?

or the float is high and its getting to much fuel

i would verify all of it before you do a bunch of jetting and find out that is not the issue

Click to expand...

if I am not mistaken, he has the stock carb, which is not a pumper.

Re: KLR You Experienced? Not really.

What's a pumper carb?

Re: KLR You Experienced? Not really.

Jimbonaut said:

What's a pumper carb?

Click to expand...

Stole this from adv rider. He said it better than I can. I don't have any dyno numbers to prove it, but I feel that my dr650 did have more mid range power as well, but that was likely not due to the pumper aspect of the carb, but likely other parts of the carb design. Anyways...

"Flat or round slides have the throttle cable hooked direct to the slides and thus throttle opening is totally based on your wrist.

CV carbs use air flow(vacuum) to open the slides and your wrist controls the throttle butterfly valve (like an automotive carb) to "ask" for throttle opening... However, the opening is controlled by CV slides based on what the engine can handle. Sort of a buffer between your wrist and the slide.

With a non-CV you can snap the throttle and fall flat as the engine is not pulling enough air and Vacuum yet to pull fuel at the rate you just asked for (with your wrist). In theory, the CV carb will prevent this by delaying the speed the slide opens to match what the engine can handle. So, smoother throttle delivery.

A "pumper" carb is a flat or round slide with an accelerator pump. This will shoot a spray of fuel every time to hit the throttle. This raw fuel helps the engine to rev faster so that the engine does not have a spot where is wants more fuel but can't draw it yet from the jets...

CV carbs are a little less picky about mid range jetting...
Flat or round slide carbs really need good jetting for best performance...

Accel #s will improve with a pumper and the snap throttle response will improve. So, if you are on and off the gas alot a pumper will seem to add horse power.

However, at wide open throttle or any steady throttle the accel. pump is doing NOTHING. So the horse power in those situations will not be more."

Re: KLR You Experienced? Not really.

Ask and you shalt receive. Thanks man, great explanation.

Re: KLR You Experienced? Not really.

The pumper isn't delivering much, if any, fuel at that point of the throttle. It's only at the bottom end when there isn't enough (or there's less) vacuum to draw fuel. The Holley on my Box Chevy allows you to change the cam so that you're getting fuel longer throughout the throttle and the pumper jets to meter the amount. Most motorcycle carbs don't seem to have those options.

Re: KLR You Experienced? Not really.

sorry about the pumper mislead i thought it was pumper

make sure that you check the aircut valve is in good shape and is not holed if it running rich

Re: KLR You Experienced? Not really.

After pulling off the carb and completely disassembling it, the only smoking gun I could find was a tear in the air cut-off diaphragm (exactly as cxman suggested as a cause). Some have suggested that the choke plunger may not have been opening/closing properly but after careful inspection I could rule that out - works fine. The jets are all stock sizes, as is the needle. Mixture screw set at 1½ turns out.

I got hold of another diaphragm, rebuilt the carb, checked the air filter was in good shape, installed a new plug and waited for the rain to stop.

Ok, please ignore everything I've ever written about Wide Open Throttle. Any diagnosis I've made, smoke I've seen pouring out the exhaust etc was made at WOT but with the bike in neutral and the engine not under load. WOT needs to be done in gear for - depending on who you ask - a mile or three. Which, it turns out, is quite a fucking thing.

Grabbed a bunch of tools I'd need, headed out to a stretch of road I figured was long enough and hopefully quiet enough on Easter Sunday, and had at it. This thing absolutely hauls ass. WOT for three miles on this bike I swear made me ten years younger. At least. Quite the eye opener.

Pulled the clutch at the end of the run, killed the engine and coasted to a gas station where I pulled the plug. Here's the scoop -



Light grey whatnot. From the diagnostic plug charts I've found online, I'm looking for a coffee colour, but light grey is pretty much on the money too, right?

The weird thing is that the bike still starts with no choke at all, even when cold. It literally leaps into life. Like there's a pool of gas in the cylinder, patiently waiting for the ignition. I know the choke is operating properly, and the main jet has nothing to do with start up. Pilot jet? Needle or needle jet? All those things are stock at the moment. The stock needle is not adjustable (I could shim it of course) but the DynoJet needle I have is adjustable.

The bike runs like a champ. In fact my man Brian who's worked on these things for thirty years says it's the best pulling and strongest KLR he's ever ridden. Would love to dial in the carb a little better at idle, but for keeping me young this thing comes up aces.

Re: KLR You Experienced? Not really.

teazer said:

Not needing choke is a sure sign that the bottom end is too rich. Fit a NEW OEM type pilot jet and try again. Also inspect the enriching system. Sometimes the "seat" is damaged and allows extra fuel in and often the choke plunger is hard and fails to seal.

Get idle and just off idle right first.

Click to expand...

Thanks man, I'm going to do that. I'll order a new OEM pilot jet and see if that leans out the bottom end. I checked the enriching system and it seems to work fine - at least the plunger does. Would checking the seat just be a visual check? If it's damaged is there any way to repair/replace it?

Just came across this article written about the Keihin CVK40 carb which is pretty informative. Thought I'd share a link in case anyone's following this thread who - like me - is learning about how these things work.

https://gadgetsfixitpage.com/article.php/the-keihin-cvk-40-carburetor

It's fairly layman which is great for me, but some of the tuning mods suggested do assume that you have a DynoJet kit. Still, it helps to explain how the carb operates, and gives some insight into how various components of the carb influence its operation.

Re: KLR You Experienced? Not really.

Good link. I think that mine has the KLX needle setup. I need to read up on these some more.

Re: KLR You Experienced? Not really.

I need to figure out my rich idle. I'm trying to source an OEM pilot jet, and I'm also trying to figure out needle settings. The stock KLR needle isn't adjustable but the DynoJet needle I have is - moving the e-clip up or down is going to have an effect on richening or leaning out the low end I think.

Re: KLR You Experienced? Not really.

There are a few different C model KLR650s, you would need to double/triple check but this one fits the early C model: https://www.cmsnl.com/kawasaki-kl650c1-klr650-1995-europe-uk-fr-nl-ar-fg-gr-it-nr-sd-sp-st_model12410/needle-jet_160091865/
Also here is the parts list I pulled that one from, there are 4 different variations that might be worth looking at: https://www.cmsnl.com/kawasaki-kl650c1-klr650-1995-europe-uk-fr-nl-ar-fg-gr-it-nr-sd-sp-st_model12410/partslist/E1611.html
Correct me if I'm wrong, but I'm guessing that you're like me in that you have a KLR650-C6 - and if that's the case, the exact Needle-jet that you're looking for is this one https://www.cmsnl.com/kawasaki-kl650c6-klr650-2000-canada_model12415/needle-jet-n8td_161871128/#pageproductModelfit and those are out of stock both here and at Bunbury, so I'm not sure where I'd look next.

Side note, thank you so very much for this thread and all the time you have put into documenting this journey. So much of my learning about the type -C has been digging through German forums with wonky translations or finding random text dumps of people explaining the differences vaugely. Your thread and how recent it is has been very inspirational to me. Thanks dude.

Edit: In the event that I misinterpreted what you were actually looking for, here is the OEM Jet-pilot for the KLR650-C6: https://www.cmsnl.com/kawasaki-kl650c6-klr650-2000-canada_model12415/jet-pilot-40_920641108/

Re: KLR You Experienced? Not really.

Hey man, really appreciate you writing that and I'm really glad this thread has helped you out in some way. You're right, this C model is rare as hen's teeth (in N America anyway) and there does seem to be very little info on it online. Fortunately it's pretty similar in terms of engine and carb to the more familiar A model, and mods like the doohickey and thermo-bob apply to both models too. I had no idea that there were a few different C models (just to muddy the waters even further!), and thanks a million for the pointers to the various parts that I may well need to source to dial in my carb.

Appreciate the kind words and insight my man, thanks a lot. Post up a picture of your ride - the more C's on here the richer this section of the forum'll be for it =)

Re: KLR You Experienced? Not really.

Dumped the bugger the other day doing about 3kmph - no harm done to man or beast but since then the rear brake is all kinds of rubbish. I've bled it, I've checked the caliper and lines, I've checked the adjust nuts on the master cylinder clevis but can't get the brake to bite. I have to hoove down on the pedal to get any kind of grab at all but I'm not sure what else I to try, other than to bleed it. Again. Any suggestions gents?

Re: KLR You Experienced? Not really.

sounds like air got it while down and you likely need to bleed again to get it out. Not sure if you can put a brick on the pedal and let it sit like that overnight to bleed like the zip tie on the lever at the bar trick. It may work.

Re: KLR You Experienced? Not really.

Maritime said:

sounds like air got it while down and you likely need to bleed again to get it out. Not sure if you can put a brick on the pedal and let it sit like that overnight to bleed like the zip tie on the lever at the bar trick. It may work.

Click to expand...

I'll try that Mike - I can't figure out what else it could be apart from air somewhere in the system. Damn if I haven't bled it for nearly an hour already, and the rear brake line isn't that long either. I can see the caliper actuating with the lever fully depressed so I'm pretty sure it's not seized, and I've tried tapping the master cylinder and line to dislodge any bubbles that may be caught somewhere - I guess I didn't realize that bleeding a brake line could take so damn long. What a pain in the ass.