To be clear, I do have a few sets of genuine ones but wanted to try some of these since i know they are prolific out there. why? why not, i paid 55 bucks a pair .
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/pk-knockoff-auction.jpg)
I had a set of RD350 carbs on there, this bike has the eBay 350 cyl's on it, so its sort of a cheap build just to try the current garbage that's out there. TBH, so far everything's been good.
It ran really well w the stock carbs but as it is, the midrange was OK, but sort of lacking. before throwing th set of dave-f modded carbs on that i have, i figured id go this way. I wanted to use the stock y-boot, so the steel adapters they have out there, sorry, suck. bad. they partially block the airjet, so i fired up the lathe and made the adapter rings out of some scrap 6061. 50mm id on carb side, 42mm ID thru the middle, 46mm OD on the y side (stock is 45). tapered the cut and radiused it so it all matched and this is what i came up with. they actually press on the carbs but I used an M4 screw to hold it just incase things shrink when air fuel runs thru them (yes regular unis would have been fine)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/pwk-to-yboot-adapter_2-rotated-e1719596552554.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240629_124911.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240628_171437.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240628_171450.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240628_172041.jpg)
as far as the oil injection, i used some spare oil nipples i had off the TZR intakes i replaced, drilled a 3.8mm hole and pressed them in the top of the carb, this can be done with a banjo and bolt, or a stock rd oil nozzle replacement as well.
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/DSCI0048.jpg)
also compared to a stock 28:
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/DSCI0052-1.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/DSCI0049.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/DSCI0051-1.jpg)
on the bike:
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240629_212744.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240629_212801-1.jpg)
test running, and playing w the needle, the jetting seems to be.. pretty spot on w/a 40 pilot (had a 38) and a 140 main (was 135) . needle that cam in the carb (no numbers but comparing to a JJH i have on hand... it looked the same) was good, would up in middle. 2nd clip, it pinged a bit, 4th clip id stumbled.
:for posterity, this bike has FPP chambers, no porting, rm100 v-force reeds, and a cdi with a curve for ignition.
plug check looks good, after about 25 miles: (on an 82 degree morning with swamp-ass humidity)
(flash makes this one look a bit whiter/grey that it actually is)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240630_101237.jpg)
(https://2strokeworld.net/wp-content/uploads/72-r5/pwks/20240630_101759.jpg)
just figured i'd share this, especially for people that aren't familiar w the pwk style carb.
:metal: :metal:
m in sc,
i have used these carbs a lot on various projects, always with very pleasing results, however, estimating initial jetting is always pure guesswork as the jet sizes use a different scale to mikuni carbs, so, my question is, in your post are you using mikuni scale or "pwk"?
cheers
les.
pwk. one thing i always aim for is using the ones with the keihin long hex (main) jets.
hi again,
this guide might be of interest to anyone thinking of using these carbs.
http://www.mid-atlantictrials.com/instal.html
cheers
les.
Interesting stuff. The owner of this unusual RZ500 engined bike was quite proud of the fact that he used $30 china carbs on it. He had to make new intakes. It sounded pretty good.
(https://i.imgur.com/NJoMv9U.jpg)
elliottles1 thats a great link, thanks.
I mean, they work great. comparing them side to side w 'legit' ones.. there really isnt any difference overall. there are, absolutely, really bad ones out there as well.
I rode the bike out last night to abieknight of sorts, ran perfect, on way home jumped on the interstate, hit 100 in 5th (it has a 6 speed in it) on the merge ramp onto 77s, and had no issues riding hwy then back into town. no ping, no surging, just.. good.
Very cool, thanks for sharing! I'm tempted to try a pair, any reason you went for the 30s over the 28s? Can you use the stock throttle cables? Genuine keihin jets? (sorry for all the questions!)
well, I knew it could pull them. 28s would have been fine though. yes use stock low top cables and yes genuine keihin brass. when looking for them make sure the spare jets they show are hex (they usually show them in the ad) and it's good to go. the round jet ones i've seen are near impossible to figure out whats going on IMHO
That's super helpful, ta!
Those chinesium carbs have definitely got better quality wise, just dont be tempted to get the ones with the see through bowls.
There are even stores selling the knock off carbs with genuine Keihin Jets, needles and springs. Not super cheap though.
https://westcoastatvparts.com/shop-1/ols/products/28-pwk-carburetors (https://westcoastatvparts.com/shop-1/ols/products/28-pwk-carburetors)
rodneya,
whats the problem with the clear bowl types please?
cheers
les.
Quote from: elliottles1 on July 03, 2024, 02:48:45 AMhi again,
this guide might be of interest to anyone thinking of using these carbs.
http://www.mid-atlantictrials.com/instal.html
cheers
les.
Wow! I just learned a lot, thanks.
Quote from: elliottles1 on July 09, 2024, 01:36:54 PMrodneya,
whats the problem with the clear bowl types please?
cheers
les.
They leak and crack very easily when tightening the bowls
ok, thought it might be a running issue.
les.
Quote from: rodneya on July 08, 2024, 09:04:11 PMThose chinesium carbs have definitely got better quality wise, just dont be tempted to get the ones with the see through bowls.
There are even stores selling the knock off carbs with genuine Keihin Jets, needles and springs. Not super cheap though.
https://westcoastatvparts.com/shop-1/ols/products/28-pwk-carburetors (https://westcoastatvparts.com/shop-1/ols/products/28-pwk-carburetors)
Wow! I am so glad I got my genuines in 2011 for $85 ea.
ive run both... tbh the finish on the cheaper ones is better than 'genuine', believe it or not.
Quote from: m in sc on July 10, 2024, 01:20:02 PMive run both... tbh the finish on the cheaper ones is better than 'genuine', believe it or not.
I'm talking about price...
there we go, £25!!;-
https://www.ebay.co.uk/itm/386182380543?itmmeta=01J2TKTMS0RFPJNSCEQDVWT0M5&hash=item59ea437bff:g:lmwAAOSwEGFlJDCr&itmprp=enc%3AAQAJAAAA0DxcOCHnpNOrduBW081x4ldwqhxyqDf9IJfe8%2BS82Ked2Sq0jL1GC1BHEEwf0N5lEsXKPlE3%2F4%2F%2B5A0XPpbmbxuNLuFiRVHgVMXnHrKTZ5hb8SwitlY2v92Mq%2BKt2Um1%2F5sFASuNcMKeJOzC8f%2FYqb8%2F9AK6puvlU8KIbEEjXQGJPxGjKd0QIlNVz2sutbg5XnxxZo8%2B28e583DP8xBYxMqN8h70r%2BAHZxYYmQP3eO1iHO639xSocoRsfh82kNWLWLHiw0%2FYtrrvWuIhfOQJ3pA%3D%7Ctkp%3ABk9SR87M6tOWZA
cheers
les.
as long as the main jet is a hex type you'll be ok. if its a round one... i wouldn't expect miracles but im sure you'd be able to get it to work.
That's because the round jet types aren't carburetors.
They're a hydraulic pipe wrench!
IR8D8R
that takes the cake. :toot:
thats bloody hilarious!!!!
Hmm, at least to my eyes, those PWKs look more "streamlined" on the air filter side than the stock VM28s. I wonder if anyone has done any flow testing of VMs vs PWKs?
Dvsrd,
i have had that thought, although i have not done any testing, they work well for me with a plain foam air filter on each.
Quote from: Dvsrd on March 29, 2026, 01:02:28 PMHmm, at least to my eyes, those PWKs look more "streamlined" on the air filter side than the stock VM28s. I wonder if anyone has done any flow testing of VMs vs PWKs?
Yes, Vm34 short bodies.
Quote from: automan on March 30, 2026, 09:02:50 AMQuote from: Dvsrd on March 29, 2026, 01:02:28 PMHmm, at least to my eyes, those PWKs look more "streamlined" on the air filter side than the stock VM28s. I wonder if anyone has done any flow testing of VMs vs PWKs?
Yes, Vm34 short bodies.
So you have tested? Equal size?
A slightly different issue regarding Mikuni carbs: Some VM30 used as OEM in snowmobiles, had same body as VM26/28. While those normally available in the aftermarket shared body size with VM32/34
I don't have any imperial proof, but im sure they flow more than a tm counterpart. to that point, I have a set of 34mm versions im going to try on the lc hybrid that currently has very well tuned to 32s on it.
I have a set of snowmobile VM34s and they are small body - not as small as a 28 but much shorter than a regular VM34.
The bad news is that they have zinc or Mazak bodies so they are a touch overweight. I did purchase "Keihin" and "Maikuni" copies and as Mark commented, the machining is way better than OEM but tolerances are not always correct and brass is iffy. The spare jets did not even have numbers stamped into them.
I have a set if small body 34s as well. and they are indeed cast from the core of a burned out star.
Quote from: teazer on March 30, 2026, 04:09:55 PMI have a set of snowmobile VM34s and they are small body - not as small as a 28 but much shorter than a regular VM34.
The bad news is that they have zinc or Mazak bodies so they are a touch overweight.
Hmm, I have come across the opposite weight phenomenon. For example, the OEM VM28 for RD350 seem pretty heavy for their size, while a single VM34 or 36 from a fan cooled Rotax 503 snowmobile engine was amazingly lightweight. Almost so you would suspect it was magnesium...
Does anyone know what material genuine aftermarket Mikuni carbs are made of?
Aluminum A383 or 360
I was under the impression that OEM carbs were cast with a zinc based alloy. I want to say its trade name is MAZAC but I cannot remember if that was the original UK company or the revised name used by Mikuni and Keihin.
I have a set of small body 34mm VMs from a sled and they weigh a lot more than aftermarket genuine Mikuni 34mm carbs. Their aftermarket carbs I believe were made with casting type aluminum. For example TZ carbs are Aluminum and RD carbs weigh more.
While I am here, has anyone tried the larger body "PWK" copies on anything? They appear to use a standard 2.60 needle jet (equivalent to Mikuni O-0) and a non standard Needle. All N427-48 needles are larger than that, so I don't know if there is another Keihin needle range in the N427-46 root diameter range but in 66mm length.
The only alternatives appear to be to drill out needle jets to an equivalent Mikuni size to suit the fatter needles or machine needles to suit. Keihin do not list needle jets for the larger PWK series unless I missed them somewhere.
I have done both on OEM keihin carbs to run on methanol in a vintage race bike, but that's back when I had access to a great machine shop with amazing inspection tools.
I have a set of 34s i plan on running on the t500 eventually. thats about it. as far as the materials, i think you're right, 'MAZAK' rings a bell, but its definately a zinc alloy. oddly the stock r5/ds7 carbs were either pure or mostly aluminum by comparison
I found this for anyone interested in Zamak or Mazak.
https://en.wikipedia.org/wiki/Zamak
Quote from: m in sc on April 17, 2026, 04:06:04 PMI have a set of 34s i plan on running on the t500 eventually. that's about it. as far as the materials, i think you're right, 'MAZAK' rings a bell, but its definately a zinc alloy. oddly the stock r5/ds7 carbs were either pure or mostly aluminum by comparison
I would speculate that the PWK34 might use the same standard 2.60 needle jet with N427-46 needles which are used on the PWK28. I'll be interested to hear what you find. stock 2.60 needle jets are available in minimum order size of 1,000 so that's probably why they are used.
the needle jet is fixed in the casting
Quote from: teazer on April 18, 2026, 11:11:58 PMI found this for anyone interested in Zamak or Mazak.
https://en.wikipedia.org/wiki/Zamak
I'm probably the only one who found this interesting. Now I have to know more about spin casting; I'm sure it has nothing whatsoever to do with fishing
Quote from: m in sc on April 19, 2026, 10:01:30 AMthe needle jet is fixed in the casting
That is probably true for a genuine PWK and would be consistent with Keihin not supplying parts. Unfortunately the knockoffs are a little different - no surprises there eh - and use the standard 2.60 needle jet as a PWK38.
I wonder what's in clone PWK34's