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Best carburetor for an 1985 KX125
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Only $10 for all 2026 SX, MX, and SMX series.
And what about a PWK 35 ? (like the later 80's KX125) more easily tunable...
That's what I was thinking but I wanted to see if anyone had other options.
Didn't Honda first use the PWK on their CR125 first before Yamaha, Suzi and Kawi went with it?
Why don't you want something more modern?
https://www.keihin-fcr.com/index.php?route=product/product&product_id=163
I might but I want to keep it period correct to be legal with AHRMA rules.
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Back in 1985 I had a KX125 that I had Harry Klemm (Klemm Research) mod for me and he only ported and did a little head work. At that point he said the stock carb and stock pipe were fine and didn't recommend any changes other than minor jetting changes. I've recently been looking for those jetting changes as I just restored one but no luck. I did find in my research that Kawasaki did change the jetting quite a bit (same carb) between 85 and 86.
Yes, it is surprising how much variance in jetting these bikes will tolerate and still run well.
I use a PWK I think 89 KX125 carb on my 1980 YZ125. I really like how it added more bottom- even compared to the smaller stock 32vm Mik round slide. The KX carb on your 85 is a good one, R-slide Oval bore. I also have this bike,,and don't think I'd make change unless the slide and slide bore where wore out to the brass.You can't buy new slides.
I use the 85 KX125 carb on my 78 RM144...installed it back in late 80s as it was best I could find to hop that engine up.
I think you may find a bump in power delivery going from the R slide 35 Mik to the 89 PWK 35,,but splitting hairs.
This link has part numbers for KXs,,,so if you see a carb advertised,,the number on side of bowl will identify it with this chart
http://www.oem-cycle.com/KX125KAWASAKIBIKEID.shtml
One nuisance with carb changes is finding the right cable and throttle. I did a quick motion pro vortex throttle with my YZ125 PWK carb swap...I think it was a big improvement.
Any luck finding jetting specs on your stock carb? I have an '85 KX125 with a fresh top end, new vortex reed cage, and PC pipe. It's not bogging, but the power seems very flat compared to what I would expect and have read on this year model. I'm thinking it's on the lean side, but I will need to order jets and start testing. I'm running a 270 main and 25 pilot currently.
Yes, the PO had the wrong needle/needle jet combo in it. Once I got the correct needle in it the bike ran much better. I fussed with the jetting going richer until the performance dropped off then went back to the previous setting. It was still running a bit rich but I knew I wouldn't race it again until November's cooler weather so I left it alone...for now. Talked to Tom Morgan since he was a Kawi man during the early 80's. He had some useful information on these style engines as far as squish and porting. He will likely separate me from my money soon.
Can you share the carb settings that you settled with?
Sure.
In the following settings the bike ran good ALTHOUGH a little rich. No blubbering but it could definitely go down one or two steps on the PJ, MJ and needle position. These setting were in hot humid weather (Mid Ohio). If the temps were 20-30 degrees cooler the jetting would have been closer to ideal. YMMV.
Temp 90 Degrees
Altitude 1000 ASL
PJ 45
MJ 330
Needle 6FJ6 (in the bottom clip/richest setting)
Needle Jet R6 389
Slide 3.0
All with the VM34SS, correct? Any major motor mods or are you close to stock?
Either way, this gives me a really good baseline to start at. Thanks!
Yes, VM34SS. I do have a DG pipe and silencer on the bike.
In 1986 Team Green recommended replacing the needle jet (not needle) with a Q-8 for better mid range performance, just figured I'd throw that one in.
Did those bikes have oval bore carbs like the earlier KX has? I can't believe how good my bike ran,no jet changes. No matter pipe or porting. I don't think my carb even has an air screw. Got a Kehein for it only because there's nothing left to play with but I probably won't put it on. It runs great
The 85 was a mid range ROCKET with the VM34SS. No need to change what isn't working unless your current carb is broken somehow. This was my bike from back in 1988:
I had both years. 85 was mid-range and the 86 was much more racey, high-end power band. Different port spec as well from 85 to 86.
I liked the handling of my 86 more, and the 85 engine more.
Pit Row
I agree the VM34SS on those year bikes worked great and those motors would tolerate a wide range of jetting. I don't know if that is because of the VM or the motors.
Swapping the carb on that bike can be a little more challenging. That VM34SS were used on the mid 80's KX125, KDX200 and Tecate 250. They had a larger OD on the motor side than the other VM34's out there. That Kawasaki one was around 43mm and the rest of the VM34s are 40mm. Airbox side was the same 58mm. If I remember correctly, the Kawasaki VM34 had a smoothbore type slide.
PWK 33 and 35s are close at the 42mm OD on motor side and 59mm air box side. But if you are trying to be AHRMA correct, PWKs didn't come out till 1988.
I know www.off-roadinnovation.com used to do PWK conversions for those era bikes, not sure if they still do.
I understand. Why? Because when I measured the ID it showed 38mm (ID) and I thought the PO had replaced the OEM carb with a 38mm. Then I did the RIGHT THING and measured the slide; bingo 34mm. Yes it has an oval bore. At this point I don't see a major advantage to go with another carb and deal with fitment and jetting.
I haven't mounted it yet,I got a 38 Kehien with a Stic. The intake fits no mods. The airbox side needed reduction.Boswell machined a spacer he pressed on and fit the airboot perfectly. It was a coincidence with a spacer the length matched stock to first right in there
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