Mikuni VM30 Question

[suey1958]

Still collecting parts and considering getting new carbs instead of using the old stock ones.
I am seeing Mikuni VM30-83 carbs that look totally different,.some look taller, some look shorter. They are both listed as VM30-83
I have heard the term LOW TOP and HIGH TOP on the forum but never knew what that meant. Is that what I am seeing as differences in these?
They are on ebay at around 75-80 dollars each and are listed as Mikuni. I also see what appears to be knock offs for a lot less money.  Also Is the choke lever normally removed from the right side carb?

[85RZwade]

I'd avoid the knock-offs. A friend ordered one that LOOKED like a PWK28, but when the time came to do a little repair, no parts were available from the vendor and nothing from Keihin (sp?) fit.
Wade

[rodneya]

I would not buy carbs off ebay at all. Way to may knock offs and bait and switch sellers
Pay a few more $ and buy from a known shop. Some places even offer jetting setup

[quocle603]

High and low tops are size of the caps that screw on the top of the carb. They have different slide height for the different caps.

Don't get the Ebay carbs. You'll have a hard time getting the proper jets and parts for them. Go authentic or suitable brand. Heard good things about the pwk but you need to avoid the shitty Chinese clones, just make sure they are made in Taiwan.

[pdxjim]

Genuine PWK28s are still available for about $100 each if you shop around

I think I got mine from partzilla.com

[Hardy]

Get ahold of supertune (chuck), he can provide a bolt on affair including correct jetting/cables ect...

At very least he will provide you the correct information to suit your project requirements.

Hardy.

[quocle603]

Genuine PWK28s are still available for about $100 each if you shop around

I think I got mine from partzilla.com

This would be an option too. Not sure about the performance boost if you're still running a stock system.

[suey1958]

Gonna check with Chuck before I buy any but This is what I am curious about,...
Both of these are advertised as genuine Mikuni VM30-83's. These are obviously different. Are these variations That Mikuni makes for the different bike brands?
It just seems to me that if you purchase a Genuine Mikuni VM30-83 that they should all be the same. Sorry for rambling on about this but my curiosity has gotten the better of me.   

[teazer]

This is a can of worms, but let's see if we can clear up a few things.

Mikuni made many different version of the same basic carb over the years for OEMS.  Sometimes it was just a change in jets and other times there were different circuits added or deleted.  Those OEM varieties typically had a manufacturers model code stamped into teh choke (enricher) part of the body.

Just to add to that confusion, none of teh specs were published by Mikuni and sometimes it's a PIA to find where the Yamaha or Suzuki published the spec and even harder to work out the differences.

Hi tops and Lo Tops are another little diversion.  Some countries had power or emissions rules that meant that the easy way to limit power was to stop the slide from opening fully.  That's easy, just make teh slide longer.  And then what do you do for countries without those restrictions.  Easy, fit the same slide and a taller top so they can open fully.  So now we have long and short slides and low and tall caps.

Aftermarket was a whole lot simpler.  Mikuni do offer a couple of different versions of some VM carbs, but my guess is that any version that is different to the version on the SUDCO (American Distirbutor) was probably not made by MIKUNI at all but is probably a knock off copy.

A buddy of mine showed me an advert for Mikuni flatslide carbs and the boxes had a SUDCO sticker on them, but the carbs were coming from China and were copies - good looking, but still copies.  AFAIK SUDCO don't source Mikuni carbs out of China and they probably don't allow others to sell them.

I would be very surprised if Miknui actually sell physically different carbs with the same part number.  That would make no sense.

[suey1958]

 Teazer says "I would be very surprised if Miknui actually sell physically different carbs with the same part number.  That would make no sense."
Thats exactly what I was thinking and if thats the case then there are a ton of knock offs out there.  Thanks for responding 

[pdxjim]

Genuine PWK28s are still available for about $100 each if you shop around

I think I got mine from partzilla.com

This would be an option too. Not sure about the performance boost if you're still running a stock system.

Tuners in the UK LOVE the PWK28's and use them on builds up to 75-80hp with no issue.

[m in sc]

i love pwk's. def buy genuine, theres even more clones of those than anything.

[pdxjim]

i love pwk's. def buy genuine, theres even more clones of those than anything.

100% agree.

[teazer]

So I have admission:  My curiosity got the better of me and I decided to buy a 40 dollar "VM30" just to see how good, or bad it was.

First impression was that the box was flimsy and the USPS had to stick it in a plastic bag to get it delivered.

Casting is nice light aluminum and machining is amazingly good.

main jet was unmarked and had a very fine thread.  It measured up as more or less a #240.

Pilot jet was almost the same as a VM22/210 but with larger air bleed oles and some swarf still inside the jet. OEM Mikuni jets are the same thread, so that was an easy replacement.

Slide is aluminum and unmarked but a Genuine 2.5 brass slide slots right in. Either would be fine, but the copy has a different cable arrangement. 

Needle is marked PZ34JA and is too lean for most 2 stroke applications.  It is almost the same dimensions as 6EJ13-53 or 6FJ41.

Needle jet is a #159 copy, but it has a marginally smaller diameter at the top and bottom, so it's a rattling good fit in the carb body and falls out where a Genuine 159 is a light pres fit. I didn't check the carb to see if a genuine 159 would fit.  I suspect it could be pressed in. It is also threaded with what I suspect is a Keihin thread pitch. I can't get to my Keihin parts right now to check, but neither Mikuni round or hex main jets appear to match.

Float jet is pressed in and I wasn't game to extract it to see if a genuine Mikuni needle and seat could be persuaded to fit.

Air jet is pressed and could probably be drilled out if neccessary.

So in summary, really nicely machined and beautiful casting but the brass and needle are on no use on a 2 stroke. They claim it is set up for a KZ440 and certainly the jets and needles would be more suited to that application.
for 40 bucks plus new genuine Mikuni brass they might work, but I have no flow tested the drillings or tested it on a bike to know for sure.

[teazer]

I managed to locate my stash of Keihin jets and the main jets from a SOHC CB750 are a perfect match for these carbs.  They are 5mm x 0.8mm