Found out I have a replacement pwk... suggestions needed

[TheScrambler]

Upon doing a carb clean and jetting to more normal sizes (previously 68P 160M, now 42P 152M), I discovered that the previous owner installed a replacement pwk (genuine keihin) on my 89. All the parts inside match what a sudco pwk35 comes stock with. The first third of the rev range and throttle seems to have absolutely no power now, like it's not even close, when it should be relatively close to just right. From my understanding, the KDX uses a unique jet block, am I correct? If so, would it be reasonable to purchase a used oem kdx pwk and harvest the jet block to swap over? If anyone has any insight into the actual difference between blocks I would love to know. This replacement came with a #6 slide and a DGK needle on the 3rd clip, which I'm thinking should be fine to get me in the ballpark. Let me know what you think

-Jon

[Chuck78]

I have never heard anything regarding the KDX having some special unique jet block. The OEM Kawasaki needles are slightly different than genuine Keihin non-OEM needles, and have their own Kawasaki nomenclature designation format. They will be labeled something like R1167, whereas genuine Keihin non-OEM-Kawasaki and some other OEM Keihin needles will have letter codes such as CEK, DEK, CEL, DEL. Those are the popular ones. Two of those work better with the OEM #5 slide, the other two work better with the slightly leaner #6 slide like you have.
The KTM 200 crowd really rave about the Suzuki RM250 triple taper needles. They'll have a 4-letter code vs 3, NECJ, NEDH, etc. I wouldn't go using the KTM 200 spec, as those have slightly larger PWK36 carburetors, so you would need to decode them appropriately as far as taper & diameters.

Besides the needles being their own Kawasaki version Keihin needles, the only other thing that's even remotely "unique" to the KDX is that it uses a PWK 35, whereas most other bikes will use a PWK 36 or for MX & a select few years of 250/300 woods bikes, a PWK 38. Some older KX125's and other 125 MX bikes use a PWK35, but the later generations of 125 2-strokes swayed towards a PWK36. The 36 & 38 are a larger carb than the 35, in terms of external dimensions in particular the air box boot and intake spigot mounting diameters.

[Chuck78]

Getting your jetting dialed and having a good new jet block gasket will make a night and day difference in the way the bike runs. It can go from running horribly, to running acceptably after a little fiddling, to running what would feel like nearly a dyno tuned factory race bike... I've experienced this before on multiple bikes, and it's l incredibly rewarding to take the additional time to get the bike really well dialed in. Keep tinkering with it, and once you get a decent baseline of brass parts established, only make one change at a time so that you can see how it affects everything. The pilot screw adjustment adds fuel through the entire throttle range, so getting that dialed in better can make a world of difference on the needle height or spec, and even one main jet size.

There is an excellent jetting guide thread pinned as a sticky in this forum somewhere, I highly suggest finding that and following it very closely.

[TheScrambler]

Thanks for the input, I'll keep the needles in mind as I go along. I ordered a used 89 model carb body this morning, as I believe it is actually different in some way from the one I currently have. I've been doing some serious sleuthing and cross referencing ths morning, with interesting findings.

Everything I'm talking about here is PWK35. You know how 89 models came with much richer jets from the factory than 90-94? There may be a reason for that. The 89 model year uses a unique serial number on the carb. 90-94 uses another serial number and 95-06 yet another.
The different serial numbers on the carb body correspond to what model they came on, and you can easily back-reference any unknown pwk using this method.

The genreal purpose sudco non air striker pwk 35 currently available is stamped PWK R70xxxxx
On the side of a genuine kawasaki keihin pwk (and probably others) there will be stamped:

PWK V###xxxx

The #'s being the important part. This goes along with the kawasaki prefix for a carburetor, which is 15001. Using any internet parts fiche, input the 3 digits after the V like this: 15001-1###, and check out the fitment, it'll tell you what model it's from. There is always a 1 before the three digits in the official part number for some reason. It's how I just avoided buying an improperly listed kx125 carb, which looks outwardly identical to a kdx pwk. There has to be a reason for the different serials, because the carb bodies are otherwise exactly the same. Hence why I think the jet blocks are different, as there is no way (that I know of) to pull the emulsion tube and look at the arrangement/height of the holes or the diameter of the needle orifice.

From my research this morning:

V465 is the 89 kdx200 carb
V564 is the 90-94 carb
V980 is the 95-06 200 carb
And V392 is an 88 kx125 carb that otherwise looks identical.

Maybe that'll help someone. Again I'm not sure that the jet block is actually different but once I get this used one in I'll report back with findings.

[TheScrambler]

Also, the reason I discovered all this is because I just went through and rebuilt the carb that was on it, including replacing the jet block gasket. I'm highly experienced with carb cleaning so I know it was all done properly and thoroughly.

I've read the jetting guide and tried to shoot for what would be somewhat close for my bike, but it feels far closer to correct with the 68P 160M than the 42P 152M, which just doesn't add up. Interestingly, the body of this carb that I have is blank where the PJ should feed into the body. All I see is the needle jet and what looks like a tiny transfer port just behind it, no larger pilot circuit hole behind the slide

[John_S]

There must be something different about the KDX carb. I haven't heard of people having problems with genuine replacement slides but its interesting that Jets R Us says "Do not use these throttle valves on PWK 35 KDX." They're referring to every slide. I wonder what it is that would make them print that specifically? The KDX and one model year KTM 300.

I have a 33 and bought a 35 air striker so no experience with the factory 35.

Screenshot 2024-01-16 175420.png (69.67 KiB) Viewed 1125 times

[Chuck78]

That's interesting, I have never seen that the KDX PWK 35 takes a different slide than the KDX220 PWK33 or any other standard PWK35.

Regardless of your 1989 specific serial NUMBER, 93-94, 95-06, they are all a Keihin PWK and will all work perfectly fine on your bike. The only exception would be the 1988 which has the choke on the opposite side. The plunger is still located on the same side, but there is a lever that does not exist on the 89 and newer KDX carbs for the 88 model.


As far as specific model years go, there was no need to buy a 1989-specific carb body unless you wanted to be able to use the exact stock jetting specs for a 1989 KDX200 carburetor, but even at that, stock jetting is usually a slight bit on the rich side especially on the needle and main jet, and always will need some slight adjusting, especially for varying altitudes, temperatures, & humidity levels. The H-series kdx's notoriously ran like a completely different bike after removal of the airbox snorkel or lid and fine tuning the jetting. Significantly better power. Stock jetting is never really exact, although the new Beta models certainly have it closer than any brand new bike that has come out for a very long time.

The genuine PWK 35 newer replacement that you have would work perfectly fine, it's better than the 1989 used carb, but would just need appropriate jetting, which takes a slight bit more time than properly jetting the original carburetor if in good condition.
There's no secret magic behind a slightly different jet block for the first water cooled KDX model year or the 5 years following it, just variations on the same thing.
If it was a 1989 only version, then 1990 through 1994 were probably improved upon.
To do some research and check the various superseded part numbers and see if the 1989 cylinder had different porting them the 1990 and later models through 94, that would tell you year by year a little better story. Different porting will require different jetting of course.


I would honestly have considered getting rid of all of them and running a new PWK 35 Air Striker variant, as this is the best version of the PWK that would be available to fit your bike directly. Order with jets/needle & slide to suit any water cooled KDX 200 PWK35 baseline, and then fine tune the jetting for your particular bike and elevation / temperature / humidity & premix ratio as well as premix oil type. Yes, even the type of oil you use can have a slight effect on the jetting, as some oils contribute more to combustion whereas others do not.

Ordering a 35-year-old carburetor used off eBay etc that is potentially very well used and worn is always a gamble. The slide tower areas definitely get wear and tear in them, as well as the carbs getting internal corrosion. Make sure to inspect it carefully for wear and tear to eliminate any head scratching later.

Best of luck Scrambler, and enjoy riding this fine machine once you get it together! Spring is right around the corner now as far as winter projects go at least! I'm already looking to plan some late March trips if not sooner! A couple buddies are planning a trip late February already to go down to West Virginia to ride Buffalo Mountain, slightly warmer there vs Ohio, but I had obligations that weekend already.
Good luck!

[TheScrambler]

UPDATE: Suspicion confirmed, there is a pretty big difference between the aftermarket genuine pwk and the KDX pwk. The Kdx has an idle circuit hole well behind the slide, whereas the aftermarket one is blanked off behind the slide, which was obvious with the jet block off. This would explain my difficulty in getting it to idle. Will post pictures in a day or two when I can take the one back of the bike for comparison. I will also compare the slides.

[Chuck78]

So where is the pilot fuel orifice located on the aftermarket genuine Keihin if it's blanked off where the KDX has the pilot orifice?
It definitely has one somewhere in the vicinity. I'll have to compare mine tomorrow PWK33 versus aftermarket genuine Keihin PWK 35 Air Striker. The Air Striker runs significantly better than the OEM once jetted properly.

[TheScrambler]

Chuck, there is a tiny bleed hole just behind the main needle jet orifice. Both the KDX PWK and the aftermarket PWK have this, but only the KDX carb has the bigger idle hole about 1/2" behind the slide. I assume it's some kind of transition port that runs off the pilot jet circuit.

[TheScrambler]

Update: I am either blind or stupid, the aftermarket pwk does indeed have the same idle hole. No idea how I missed tat the first time. And in fact I visually can't tell the difference between the two. The oem pwk slide does seem to have a slightly better fit but otherwise is identical. The needle valve is a 3.2 instead of a 3.8 though, unless there's something different inside the jet block they are otherwise the same. Either way, put the 89 pwk on with a 155 main, 45 pilot, dgk needle on clip 2 and it seems to be running well now. However the plug insulator is just barely darker than white now which scares me a bit. As it came to me it would blacken but not foul the plug.

[SS109]

Update: I am either blind or stupid, the aftermarket pwk does indeed have the same idle hole. No idea how I missed tat the first time. And in fact I visually can't tell the difference between the two. The oem pwk slide does seem to have a slightly better fit but otherwise is identical. The needle valve is a 3.2 instead of a 3.8 though, unless there's something different inside the jet block they are otherwise the same. Either way, put the 89 pwk on with a 155 main, 45 pilot, dgk needle on clip 2 and it seems to be running well now. However the plug insulator is just barely darker than white now which scares me a bit. As it came to me it would blacken but not foul the plug.

I don't know if you're doing it but most read plugs incorrectly. You have to read the base of the porcelain and not near the tip. Check out this thread for pics showing examples: viewtopic.php?f=105&t=21813