Real 20mm Carburetors vs fakes - with pictures

[GrumpyUnk]

Well, the thread got a bit of new life, so I will report that a second order from Glixal(aliexpress version) of a 20mm showed up a month ago, and it had the 'step' in the bore down near the venturi/butterfly. I sent them a picture of the previous order for the same item, showing it had no 'step', and they refunded my money. The person doing the words was ignorant of their product line, and I had to show with images what was 'different' and therefor not as advertised. FWIW. They stood by their product in this case where it was not correct.
I will likely use this carb in a Frank machine. (put together from 'other' parts)
tom

[jer]

Wow, Matt, burning bridges?  Any bridge burning here is being done by you, I only posted facts.  Are you saying you would have rather the members didn't know these facts?

You make many statements that are only assertions.

I'm wondering if anyone ever uses Dellorto carbs?  When you buy a 20mm Dell'o, 20mm is the smallest dimension in the air path.  This is not an assertion, anyone with any Dell'o carb can measure it right now.  What about Mikuni?  All the Mikuni carbs I've ever installed or serviced have a TRUE measurement also.  And how about S&S?  When S&S says their carb has a 2 1/16" throat, don't bother measuring it...that is the smallest dimension in the air passage.  The problem here is that these products are not Italian or Japanese, or American (all high quality manufacturers) they are Chinese!  Which isn't bad in itself, except that they didn't develop them.  They are just copying them, and this 20mm carb is a myth, a copycat concoction (that is why there are so many flavors of this fake.)  If it isn't a myth, why can't anyone get an authentic Keihin 20mm CVK?  Try contacting Keihin North America and listen for yourself what they have to say.

Oh, and lets get this oblong passage nonsense straightened out.  The attached pics, taken from three angles, show the intake air passage to be round.  And because I needed to go back and retake them, I tightened the mic down closer to the actual size, which isn't even 17mm.

And I got your dog whistle at the end about not returning the carb.  I can use it on a PUCH MAXI that could use a new 16mm carb.

[jer]

These are the pics I referred to above.

[fugaziiv]

Aug 29, 2019 11:58:28 GMT -5 jer said:

Wow, Matt, burning bridges?  Any bridge burning here is being done by you, I only posted facts.  Are you saying you would have rather the members didn't know these facts?

You make many statements that are only assertions.

I'm wondering if anyone ever uses Dellorto carbs?  When you buy a 20mm Dell'o, 20mm is the smallest dimension in the air path.  This is not an assertion, anyone with any Dell'o carb can measure it right now.  What about Mikuni?  All the Mikuni carbs I've ever installed or serviced have a TRUE measurement also.  And how about S&S?  When S&S says their carb has a 2 1/16" throat, don't bother measuring it...that is the smallest dimension in the air passage.  The problem here is that these products are not Italian or Japanese, or American (all high quality manufacturers) they are Chinese!  Which isn't bad in itself, except that they didn't develop them.  They are just copying them, and this 20mm carb is a myth, a copycat concoction (that is why there are so many flavors of this fake.)  If it isn't a myth, why can't anyone get an authentic Keihin 20mm CVK?  Try contacting Keihin North America and listen for yourself what they have to say.

Oh, and lets get this oblong passage nonsense straightened out.  The attached pics, taken from three angles, show the intake air passage to be round.  And because I needed to go back and retake them, I tightened the mic down closer to the actual size, which isn't even 17mm.

And I got your dog whistle at the end about not returning the carb.  I fully intend on installing it, but on a PUCH MAXI that could use a new 16mm carb.

Alright my man, you obviously want to be angry about this. I wasn't whistling, I was saying to toss it on before blowing us up publicly. You might be surprised that it actually does what it's supposed to, regardless of what you're assuming based on measuring the choke point instead of the actual intake measurement, which is what the titling is based on for all of these small CVKs. If you don't want it, send it back. I was never trying to imply that we'd refuse a return. We stand by all of our policies.

I've measured these, QC'd them personally and know they're good and marketed correctly (and even just did so again before jumping back into this mess, which in hindsight I should not have done) and stand behind them.

So yes, I'm entirely comfortable marketing these to the forum as a 20mm, and the folks that have purchased these from us are for the most part happy with them. Sorry that you disagree.


Matt

[Deleted]

Why would't you use 24mm carburator (152QMI)? Those are 22mm real.

[dexameth]

So I wanna jump in here and just show what I found. Matt is totally correct, but backwards on the venturi shape idea. Feel weird correcting my own boss... But look at these pics showing the difference between a stock replacement vs the aftermarket 20mm.

Intake side



Butterfly removed showing venturi step



Butterflies



Another post to follow, need to upload a couple more pictures.

[dexameth]

Well my makeshift tool to measure the intake side isn't showing up on camera that well. If you measure the height of both intake sides, they are almost identical. The 19mm carburetor has a skinnier bore than the 20mm allowing more air flow from the start. Sure, both carbs have the step in the venturi, it's how the CVK carbs are designed - it helps draw the fuel up out of the atomizer for better fuel atomization.

Yes, PWK carbs have a straight-through design... because they are of a different design; exactly that. Most PWK carb slides will have an angle or cutaway that will add the venturi effect creating that vacuum needed to pull the fuel up and atomize it.

So now we see that the 20mm carb actually does not have a step PAST the butterfly, it's the same size bore til the end (unlike the clones you see on Amazon and eBay) and actually measures 20mm. Same with the 19mm. The butterfly measures 19mm as does the bore til the end.

All in all the 20mm carbs are in fact and upgraded, larger aftermarket carburetor. I'll stand behind the carburetors fully.

[dexameth]

Aug 29, 2019 12:54:04 GMT -5 @asterix said:

Why would't you use 24mm carburator (152QMI)? Those are 22mm real.

Because some of these engines only have a 19mm port on the head, so the 24mm isn't really fitting. If you use an SSP-G racing head with oversize ports then by all means run that carb. I do, and it's great! 

The carbs can and do work with the smaller ported heads, but there's a lot of turbulence going from a 22mm intake to 19mm port in the head.

[fugaziiv]

Aug 29, 2019 13:54:46 GMT -5 dexameth said:

Well my makeshift tool to measure the intake side isn't showing up on camera that well. If you measure the height of both intake sides, they are almost identical. The 19mm carburetor has a skinnier bore than the 20mm allowing more air flow from the start. Sure, both carbs have the step in the venturi, it's how the CVK carbs are designed - it helps draw the fuel up out of the atomizer for better fuel atomization.

Yes, PWK carbs have a straight-through design... because they are of a different design; exactly that. Most PWK carb slides will have an angle or cutaway that will add the venturi effect creating that vacuum needed to pull the fuel up and atomize it.

So now we see that the 20mm carb actually does not have a step PAST the butterfly, it's the same size bore til the end (unlike the clones you see on Amazon and eBay) and actually measures 20mm. Same with the 19mm. The butterfly measures 19mm as does the bore til the end.

All in all the 20mm carbs are in fact and upgraded, larger aftermarket carburetor. I'll stand behind the carburetors fully.

Thanks Tyler, I appreciate you doing a better job of articulating this situation than I did. I'm more than happy to accept when I'm wrong.

Anger typing does me no favors. ¯\_(ツ)_/¯

Tom here at work also put into perspective out of all of the crap I have to deal with and get angry over but don't, this really is way low on the list as we put the work in to ensure that our parts are good, and if they aren't we correct the situation. Thanks Tom.



Matt

[SMALL CC TEK]

Matt gave you some good advice toss it on first ! Your combo may like that carb and it might perform better than you think you just have no idea till you try. I have done it several times myself you measure one out and it seems small yet it out performs your stock same jets floats float settings and everything ! So if you have the green light to try it and he will still take it back after you try it i would ! You have nothing to lose but some time and your in the same boat anyway it could work well..

[benji]

www.partsforscooters.com is an excellent place to buy parts. They stick behind their parts and always offer to return them. I remember a few months back when Matt went through this with someone else. he pulled all of his product and stop selling it until he contacted the manufacturer and had them explain it to him. Cvk carbs are different from most carbs on scooters, and have strange shaped bores. Personally, I don't really like them because of how different they are. but if Matt is saying it is 20 mm, I guarantee you it's actually 20 millimeters. Measure the entire area of the pass-through, and then measure the area of a 20 mm circle. Then let us know if it's different. I bet you it's not.

[jer]

Matt, I'm glad you're toning down on this, it was never a bridge burning thing. And I don't need to return it, I really do have a MAXI that needs a 16mm.

What I'm seeing here is a lot of word wrangling going on here.

Can we all agree that the air intake is ROUND and LESS THAN 17mm??? or do my pics somehow lie?
(MATT, TYLER, & BENJI, if you would humor me and either agree or disagree I think we will be able to come to some conclusion about this whole idea of TRUE or Fake.) I'm asking you three because you guys are the retailers.

So this is step one: FACT or FICTION?

[jer]

Aug 29, 2019 20:36:57 GMT -5 benji said:

Measure the entire area of the pass-through, and then measure the area of a 20 mm circle. Then let us know if it's different. I bet you it's not.

Benji:  Can I ask you to look at my pics again?  Isn't it clear that the air intake opening is ROUND?  If it wasn't round, wouldn't my paper measuring thingie have made it apparent?  And the mic plainly shows the thingie to be 16.7~mm, right?  Then how can you say you bet it's not different from a 20mm circle?  For real, how could a 16.7mm circle have the same area as a 20mm circle?

And I agree that PFS is a great place to buy parts (almost as good as the new warehouse in EC,) that's why I agonized about posting up these facts, I thought Matt might take it as an attack and get defensive.

[jer]

Aug 29, 2019 13:54:46 GMT -5 dexameth said:

The 19mm carburetor has a skinnier bore than the 20mm allowing more air flow from the start.

I'm really sorry to put up all these posts but I can't continue without clarifying this statement.

If the 19mm has a skinnier bore than the 20mm, how can it allow more air flow?

Again, I'm really sorry for so many posts, I'm only trying to keep up.

[benji]

Aug 29, 2019 21:47:26 GMT -5 jer said:

Aug 29, 2019 20:36:57 GMT -5 benji said:

Measure the entire area of the pass-through, and then measure the area of a 20 mm circle. Then let us know if it's different. I bet you it's not.

Benji:  Can I ask you to look at my pics again?  Isn't it clear that the air intake opening is ROUND?  If it wasn't round, wouldn't my paper measuring thingie have made it apparent?  And the mic plainly shows the thingie to be 16.7~mm, right?  Then how can you say you bet it's not different from a 20mm circle?  For real, how could a 16.7mm circle have the same area as a 20mm circle?

And I agree that PFS is a great place to buy parts (almost as good as the new warehouse in EC,) that's why I agonized about posting up these facts, I thought Matt might take it as an attack and get defensive.

that's part of your problem. Not trying to judge you, but you are assuming quite a few things here. Number one, you're assuming that bores perfectly round. Unless you measure it from multiple angles, you honestly don't know if it's oblong or not. On top of that, if I were you and I really wanted to know the truth, I would ask Matt how to measure it. He will tell you exactly how is rated as a 20 mm car. In fact, I believe he already explained it.

Or, you know, DROP.THE.CVK.STYLE.CARB.AND.GET.A.PWK. we're trying to go faster, right? Or are you trying to build a clone of a stock motor? Stop comparing OEM style parts to OEM style parts and start using high performance stuff. Or, listen to the people who sold it to you.

Just my opinion.